Some tips will be –
1. Make a point that one would not visit web sites such as mass advertising web sites as they are usually infectious with ad-wares and browser hijackers
2. Switching on those pop-up blockers. This would reduce the chances of a malicious ad-ware/spyware process getting run. most of the web sites (not the ones that use AJAX) opens pop-ups to fork processes.
3. Avoiding any software installation that says anti-spyware and is free
4. Do not open any e-mail that is inherently an advertisement and not set to you by your interest
I have been following this for last 2 years and I am free of any spy wares and my computer runs considerably fast. As many posted, children should be taught about the potential harm caused by spywares and precautions to be taken to avoid them. They should also be educated about the difference between spywares and parental control and monitoring software. There should be strict control of entry to online games sites and pornographic sites that churn in those 90% of spywares.