Software that scans your system for known adware, spyware, and browser hijacking. Some can even detect when you are downloading software containing adware or spyware and warn you before you download it.
Be careful about what you download. No matter how good your antispyware software is, it probably wont find all of the spyware and adware on your system. You might consider installing two or more antispyware programs in order to get better coverage as each has a different list of what they check for. Of course if you don't download software from the web then you wont be downloading software that contains spyware or adware.
Read End User Licence Agreements (EULAs) to see what you are agreeing to.If the licence agreement says that you agree to their installation of their spyware or adware on your computer then you only have yourself to blame if you go ahead and install it.
Often running the adware/spyware removal software will stop some of your downloaded software from running. If it is adware (and not spyware) that the program relies on for its operation then you need to consider whether it is worth reinstalling the adware in order to use the program in return for giving up some of your privacy.
Two recent reports that I have read regarding adware/spyware give the average number of such that are installed on each computer as 26-28. Since anyone who regularly runs scans and removes such software should have well under this number on their system you can just imagine how many are on an unchecked system. Just visiting some web sites is enough to install adware in the form of a third party cookie onto your computer that allows the advertiser to track which web sites you visit that contain their ads. You should consider turning off support for third party cookies in your web browser since most such cookies are set by advertisers sites. First party cookies from the site you are visiting rately do any harm and are often required in order for you to access all features of the site properly.
Since some adware/spyware can get installed on your computer without your knowingly downloading anything, you should run such programs on a regular basis - perhaps weekly.
This article written by Stephen Chapman, Felgall Pty Ltd.