Practices to AVOID
1: Do not fail to keep your internet programs and your computer updated!
Many of the updates for both Windows and Windows programs are security updates that your PC needs to stay current in the battle against malware. Don't put your PC and yourself at risk, KEEP IT UPDATED!

2: Do not have more than one active antivirus (AV) program on your PC. Two active AV programs may conflict with one another rendering you defenseless. Use Programs and Features in the Control Panel or Apps and Features in Win 8 or 10 PC Settings to uninstall extra programs you don't want, or need.
    Unactivated Windows Defender in Windows 8 and 10 and/or on-demand virus scanners such as Malwarebytes do not count as active antivirus programs.

3: Do not use unsafe email practices. (Where do I start?)

Programs:
    Windows Mail and Outlook Express seem to invite spam.
    Windows 7 - Windows Live Mail, Yuck!
    Windows 8 Email - "It's too pooped to POP!"
    Use Outlook (if you have MS Office), Web Mail (Outlook.com, gmail, yahoo mail, etc), or Mozilla Thunderbird!
Use the latest updated versions of desktop programs, if at all possible for maximum protection.

4: Do not open email attachments you haven't manually scanned with your virus scanner.
However, However, it has been demonstrated that some malware files fail to be detected by some malware scanners.

5: So, Do not open email attachments you were not expecting, no matter who they appear to be from. Be Safe! JUST DELETE THEM!!

6: Do not respond to spam email messages. Be wary about using using unsubscribe links (just mark message as junk) and never click directly on links in email messages. Again, just delete them!
    If you have won a lottery, a gift certificate, or received an inheritance you should certainly know it, without having some spam email informing you.

7: Never visit questionable websites (ie porn, warez, hacking) However if you must download files from these sites use discretion, scan all downloads with your up-to-date antivirus program as soon as download is complete. If files are compressed, scan again after decompressing or extracting!
    Perhaps you've noticed the Scan command in the context menu when you right-click any file.

8: Do not poke unnecessary holes in your firewall by clicking 'Allow' every time some program requests access to the Internet. When it doubt over whether or not to allow some program, use Google to find out what it is and whether or not it needs access to the Internet. Otherwise, denying access is the safest course of action, since you can always change the rule later if something does not work as you expect.

9: Never download programs and files from questionable sites. Use Filehippo (safe) or search with Google or Yahoo to find out what others are saying about a site before downloading any software or files.

10: It's not a good idea to use file sharing or P2P programs. (Torrent sites are filled with malware.)

11: Do not use pirated programs. You have no idea what the creators have placed into these programs. There are too many free programs available to take such chances. See my Freeware page at http://www.greenthumbnsy.com/freeware.htm

12: Never connect to unknown devices. Don't plug strange USB flash drives into your PC.
If you find a flash drive laying around in a public area just trash it.
Be Wary.
If you found a bottle of aspirin on the floor of a waiting room, would you keep them to take the next time you had a headache? Of course not! There's no telling what could be in those pills. Same with the USB drive. There's no telling what could be on it.
Virus? Ransomware? No telling.
Garbage cans were made for things like this. Better to be safe!

Also, never disconnect USB devices from your PC without using the Safely Remove Hardware feature in the notification section of the Windows toolbar. This ensures the drive has quit any activity so you can safely remove it without data loss or damage to the USB device itself.

13: Never use Registry cleaners or optimizers unless you know EXACTLY what you are doing. No matter what anyone says you cannot magically gain great speed increases from using these programs. Leave the Windows Registry alone until you gain more knowledge about how it works. You can easily render your PC unusable by poking into the Registry.

14: Do not use the same password and/or username for every internet site you login to. If a hacker were to gain access to your username and password for one site then he (or she) would be able to login to any site you use and possibly create enormous problems for you.

15: Don't click on any bogus popup ads - especially if the ad says your PC is infected with a virus. Close the window or turn off the browser. Use Alt+F4 or the Task Manager to close the program if necessary. It's better to take the time to restart your PC than to take a chance of getting PC malware. At best you'll need to spend your valuable time researching and dealing with the problems or at worst you may need to replace your operating system, potentially losing files and installed programs.

If you think your PC may be infected run your antivirus scanner or Malwarebytes to find out for sure. Don't take chances with your security!!

16: Never provide any passwords or personal information in response to any message, email or a phone call, informing you that your account(s) were hacked or compromised. Deleting all such emails or ending the phone call is an appropriate response.

Windows XP is obsolete!
17: If you have an old PC which is still running Windows XP I strongly advise you NOT to connect it to the internet any longer. Windows XP is no longer being supported by Microsoft with critical security updates and is vulnerable to malware intrusion and hacking to a much greater degree than later operating systems.
If you cannot afford a new PC, internet device, or chromebook I suggest you replace Windows XP with a secure and FREE linux operating system such as LXLE or Puppy Linux.
If you need help with purchasing a new PC see my page How to buy a "Cheap" PC.

Things you SHOULD do

1: Topping the list of the things you should do is to create recovery media (DVDs or USB Flash Drive) for your new Windows 8 or Windows 10 computer. PC manufacturers typically no longer include recovery disks with new PCs.
    Also, make regular backups of your personal files.
    If your PC's hard drive quits you will be glad you did.
    See my page Backup your PC to learn how.

2: Either disable all extensions (browser helper programs) in Internet Explorer or use a non-IE web browser. Mozilla's Firefox and Google Chrome are much better alternatives. Even the aggravation called Windows Edge in Windows 10 is more secure than Internet Explorer.

3: Always have an up-to-date antivirus program running. There is no reason not to have one since it is not necessary to pay for a good antivirus program. Good ones are available from Filehippo. (See my file Freeware to identify and locate them.)

At least use Microsoft Security Essentials for Vista, & 7 or Windows Defender for Win 8 and 10. If every PC had a decent security program running many hackers might need to find another line of work.

4: Always have a firewall running. Windows firewall should always be on unless you have a router or gateway that includes a firewall. Note: Running two firewalls may slow your connection speed.

5: Always use Windows Update to download and install all the latest Windows updates, including all security updates, from Microsoft. Service packs should ALWAYS be installed. They frequently contain security updates that will ONLY be found in that service pack.

6: Always delete all unsolicited emails containing attachments without reading. Curiosity killed the cat. (I know, I mentioned some of these things earlier. But people can't hear it enough. It's important.)

7: It is a good idea to manually scan all email attachments with your antivirus program, regardless of whether it's supposed to be done automatically.

8: Always copy and paste URLs from email messages into your web browser. Don't simply click on them! If they don't look right turn off your browser rather than going to a potentially dangerous site.

9: Always inspect links copied and pasted into your web browser to ensure they don't seem to contain a second/different address.

10: Always backup your data files. In Windows 7 and Windows 8 you can create a system image that backs up your entire drive if you have a large enough backup disk. It's a good idea, especially if your hard drive contains irreplaceable or valuable data. At least get a USB Flash drive or use a free service like Microsoft Onedrive to backup your personal data.

11: Always download programs and files from reputable sources only. Filehippo, and others like it scan all their files and programs for viruses and malware before offering them for download. See my Freeware page to find good free software.

12: Watch the installer when installing new software - especially freeware. At times these installers will attempt to install software you neither want nor expect. Decline all extra software installs.

13: Keep your software updated.
    Especially internet programs such as Adobe Flash player & Reader, Internet Browser Software, and Oracle Java. Updates for these programs are normally offered for the express purpose of closing security holes. Don't ignore the update prompts for this type of software.

A note concerning Adobe Reader and Java.
    Internet helper programs such as Adobe Reader and Oracle Java are not essential.
    SumatraPDF is a good, safe, and fast alternative for Adobe Reader.
    Oracle Java is not necessary for general internet surfing. Very few sites require Java now and very few programs need Java to function. These sites and software programs have many good alternatives.
    So if you wish to uninstall Java to avoid its problems, feel free to do so.

    If you want to speed up your PC disable unnecessary startup programs and/or install more Random Access Memory (RAM). (RAM is not that expensive now.) See Is your PC running Sloowly Now? for help.
    If you really want to energize your PC install a Solid State Drive (SSD). They are a bit on the expensive side, but well worth your money if speed is your object.

Other things you should avoid.
1: Do not send attachments in emails unless they are requested.

2: Do not use stationary or any other kind of special formatting in emails.

3: Do not TYPE IN ALL CAPS.
    This is considered shouting, especially in web forums.

4: Avoid texting speak in forums.

5: Do not poke sleeping bears.
    Most REAL hackers are quite content to leave you alone unless you make them take notice of you. No dinky little software firewall or consumer grade router is going to keep them out of your system. So do not go to some hacker website or chat room and start shooting your mouth off unless you're prepared to accept the consequences.

6: Avoid using online registry or PC check sites.
    Most of these sites and programs are scams, and sell you something you don't need. Most of them report non-issues in an attempt to boost the number of "issues".
    Sometimes using these programs can lead to a non-functioning computer. There are some reputable sites such as online malware scans from some of the top antivirus vendors, but before using any other check it out!

7: Another last warning about Windows Registry.
    The Windows registry is not some mystical black box of untapped performance tweaks for Windows that will lead to untold improvements in system performance.
    Most of the tweaks will lead to very modest performance gains of 1-2% tops, and probably less than 10% all combined. There is also a good chance that you will render your system unbootable if you make a mistake when editing.
    Registry default settings are set that way for a reason. Just do yourself a favor, and forget you ever heard of the Windows registry until you have gained sufficient knowledge of the dangers of Registry editing.
BE VERY CAREFUL! Data loss and re-installing Windows is NOT fun.

If you should get a computer virus or malware on your computer use another PC to access internet help forums - such as Bleeping Computer - for advice on how to get rid of it. Quite frequently the advice you will receive will require that you have more than a passing knowledge about computers. So if you would rather have a technician solve your problem for you, be sure of the charges before leaving your PC with him.

Disabling Startup Programs
Unnecessary startup programs slow the startup of all PCs and since these programs are always running in the background they use valuable RAM memory that may be in short supply, especially on many older PCs with little RAM installed.

It is possible for a user to run the system configuration utility program (MSconfig.exe) to disable some of these unnecessary or unwanted startup programs. However the best way to rid yourself of troublesome startup items is to change the settings of these programs or as a last option, uninstall the programs that put them there in the first place.

If you prefer to use a third-party utility then download a program called Ccleaner from Filehippo.com. Ccleaner is for beginning to moderate users

The Ccleaner program also does a very acceptable job of cleaning the trash files from your PC. However, it does have a registry cleaning feature that I do not recommend using unless you have more than a passing knowledge of how the Windows Registry works.

AutoRuns for Windows is also recommended. (download it from Microsoft Technet). Autoruns is for advanced users. Be careful with this program!

To learn how to safely disable unneeded startup programs see my page Is your PC running Sloowly Now.

Last things
In Windows 8 and 10, the revamped Task Manager now includes Tabs, including one called Startup which includes the feature to control and disable startup items, very handy! MSConfig is no longer necessary for this and it's startup tab redirects the user with a link to the Task Manager. Right-click the task bar then choose Task Manager, then click More Details to see all the Tabs.

The benefits of being paranoid
    Traditionally, paranoid people have been critized for believing that everyone is out to get them. These criticisms may have had some validity in the bygone era of personalized relationships since it has always been assumed that the great majority of people are reasonably honest and are not normally out to take unfair advantage of others.
    The age of instant communications, computers, and the internet has changed that. Now it is reasonable and even fashionable to be paranoid because you don't just think, you know, there are many others out there who are out to get you and your money.
    If someone you don't know contacts you it is perfectly reasonable and likely much safer for you to disbelieve them.
    For example, If you get a telephone call from someone who claims to be a banking official you know they are lying since banks never call or email their customers, they simply send you a letter in the mail. Likewise, if someone calls claiming to be a Microsoft employee you should immediately hang up on them since Microsoft will never contact you saying there is a problem with your computer.
    Hackers and scammers know your telephone number and/or your email. They are constantly trying to trick you into devulging your valuable personal information with the goal of stealing your identity then ripping you off. Don't be a sucker and be their latest victim. Just delete the email or hang up!