Tips on how you can avoid Spyware and Adware:
Many companies offer software that clear spyware and adware from your computer. Please note that these programs are different from the more-well-known anti-virus software applications.
Ensure that the security settings on your browser do not allow programs to be installed without your permission. By default, most browsers should alert you when you are about to install a program. If you are unsure of a particular program, terminate the installation process immediately.
Unless it is necessary, please avoid downloading unknown programs or software, which are available for free on the Internet. Some of this software often comes with adware and spyware.
These programs are notorious for causing spyware and adware problems. Examples are Napster and Kazaa.
You can usually do this by using a search engine to look up on the program. Read reviews sent by other users if possible on computing magazines or on reputed websites.
Reference
How to Protect Your Computer from Spyware and Adware?
http://www.microsoft.com/athome/security/spyware/spywareprevent.mspx
How to Prevent the Online Invasion of Spyware and Adware?
http://www.internetworldstats.com/articles/art053.htm
How to Find, Remove and Prevent Spyware, Internet Intruders, and Pop-Ups
http://chinese-school.netfirms.com/computer-article-spyware-pop-ups.html