Security

Backups

To avoid the lonely, disabling pain and regret that accompanies the loss of computer data, family pictures, emails, school work, you MUST BACK UP, NOW!!!. ALL hard drives eventually fail. So will yours, usually randomly and arbitrarily, and (in our modern world of making everything as crappy as possible,) much sooner than you'll expect. I see this many times a month.

Teenagers

I am not talking about your teenage son, but if some other teenagers are sharing your computer you should virus-protect that computer like it is the shared computer in the prison library. You can't stop the sun from rising, but you can wear sunscreen. Better yet, give them your old computer and buy one that only you use.  Also, installing more than one anti-virus causes problems. Just use one good one.

Antivirus

If anyone recommends McAfee or Norton/Symantec write those people off as suspicious or confused. I could spend pages telling you all the ways these programs can screw up your computer. Suffice it to say this, these programs are bloated, slow, expensive, and get this, DON'T REMOVE THE VIRUSES!

Fear

Fear mongering about "privacy and identity theft" is largely industry hype designed to break into your wallet. I am not saying that identity theft doesn't occur, but that it occurs in ways that aren't made safer by using software products sold to protect your privacy. Nor does it usually occur from your computer. Relax.  Here's all you need to do:

Scumbags

Any “tech support” that you are inspired to call from an ominous warning on your computer is bogus. Any ominous calls you receive that scare you about your computer are bogus. Never let anyone remotely connect to your computer! If you did not specifically go to the company website, (dell.com HP.com xfinity.com etc.) and find a tech support number directly on that website, then you are talking to fake tech support.

Privacy

The Edward Snowden leaks about the NSA confirm that we have none. Nothing you do on the internet is private, period.  At some point in the near future ISP’s and others will probably start making encryption software available that is easy enough to use for the average person. Until then assume that anything you communicate through the internet may someday be released by someone disgruntled.
A possible scenario is that a hacker or a government worker will release a large amount of illegally collected personal emails to make a point about how much info the government actually collects on it’s citizens. It may happen, because that is the only thing that will make the seriousness of the issue real for the average law abiding citizen who thinks they have no reason to worry if they are not breaking the law.  

My friend Zeke wrote a great post about simple ways to protect your privacy.