Back up everything! You are not invulnerable. Catastrophic data loss can happen to you -- one worm or Trojan is all it takes.
Choose passwords that are reasonably hard to guess -- don't just append a few numbers to a no-brainer. Always change default passwords.
Use an antivirus product like AVG or Norton, and set it to update daily.
Update your OS religiously and be vigilant in applying all security patches released by the software manufacturer.
Avoid hacker-bait apps like Internet Explorer and disable automatic scripting on your e-mail client.
Use encryption software like PGP (pretty good privacy) when sending sensitive e-mail. You can also use it to protect your entire hard drive.
Install a spyware detection app -- or even several. Programs that can be set to run frequently, like SpyCop, are ideal.
Use a personal firewall. Configure it to prevent other computers, networks and sites from connecting to you, and specify which programs are allowed to connect to the net automatically.
Disable any system services you're not using, especially apps that could give others remote access to your computer (like Remote Desktop, RealVNC and NetBIOS).
Secure your wireless networks. At home, enable WPA (Wi-Fi protected access) with a password of at least 20 characters. Configure your laptop to connect in Infrastructure mode only, and don't add networks unless they use WPA.
Hackers are becoming more sophisticated in conjuring up new ways to hijack your system by exploiting technical vulnerabilities or human nature. Don't become the next victim of unscrupulous cyberspace intruders.