Facebook is serving ads based on stuff I viewed elsewhere. How do I prevent facebook from snooping on me?

[kaligus]

Using a good browser is a start (I use Firefox with some additional addons to *HELP* avoid cross site tracking) and then configuring it for privacy instead of the default share my life with everyone I visit so the corporations can make more money settings most browsers (even the good ones) ship with.

*NOT* using toolbars, and ad supported search engines while impractical or inconvenient is also a good idea if you want to stop leaving your breadcrumbs every site you visit. This boils down to the price you pay for the convenience offered by such sites/tools is your privacy.

Regularly cleaning your cookies is another good idea. I have my browser set to clear all but the cookies I select as exempt each time I close the browser. (Cookie monster helps with this)

I also use "noscript" configured to block known offenders in that category (and facebook uses nearly every method possible in the hope of getting past at least one of your blocks).

Then I use an addon called "greasemonkey" with scripts to block even more ads.