3. Even if your computer is secure, miscreants depend on your trust. Be suspicious of messages, files, software; even if it appears to come from a person or company you trust.
Anti-spam, anti-spyware, anit-virus, anti-phishing tools can help. But don't assume because you are using them, you can click on everything and still be safe. The miscreants are always finding new ways around them.
It may just be human nature, but people seem to engage in more risky behavior when they believe they are protected.
4. If your computer is compromised, unplug it until you can get it fixed.
Its not going to fix itself, and ignoring the problem is just going to get worse.
5. Paying for AV software is not a solution, no matter how often it's been on TV. (Norton - the antivirus software one finds on virus-infected computers)