There are several basic rules to assure that your security on a computer is not compromised.

• Install a anti-virus/spyware program on your computer. There are many programs to choose from that will provide you with protection. Do not discount the free ones, Microsoft has a free program called Microsoft Security Essentials that works well. The program should update itself regularly and be easy to run. If you don't update the anti-virus program on a regular basis then it will not protect your security. It should not slow down your computer but work in the background watching for malicious software. You should also install Malwarebytes on your system to protect you from malicious malware.
• Never ever click inside an email unless you are absolutely sure that the URL is a trusted site. The status bar on the browser will tell you what site you are going to access. Make sure that the address on the status bar is the same address you want and not a malicious site. Phishing email (e.g. mail that looks like its from your bank but really is not) uses this technique to trick you into giving personal data about yourself.
• Never click on an attached file to an email unless you are sure of the source. Be careful of family and friends, even though they may mean well, they can inadvertently send you an attach file that can damage your computer or steal you identity. It is better to Google the site they sent you and see if it is safe. Use the software add-on called "Web of Trust" to verify that the site is safe.
• If they send you an attached file such as a gif or jpg picture it is probably okay if it was taken by them. It is best to make prior arrangements with the sending party before clicking on a attached file. Always scan an attached file by right clicking on the file in Windows Explorer (not Windows Internet browser) and select "Scan with Microsoft Security Essentials" or any anti-virus program listed.
• Always use Firefox, Google Chrome, or Safari for you browser. You should not use Internet Explorer. Internet Explorer versions 6, 7, 8, 9 has the worst rating for know unpatched vulnerabilities. Zero for Chrome and Firefox.
• You should always have the latest stable version of a browser. Here are the latest versions as of June, 2011: Chrome 12, IE 9, Firefox 5, Safari 5, and Opera 11.
• If you are using Windows on a PC don't login as administrator. If you want to disable your anti-virus software or turn off your firewall to install a program go to this web site: Bleeping Computer