[kolme]

Hardcore people in the security circles do all their serious stuff inside one-use-only virtual machines, once their stuff is done, the machine is deleted and shredded.

That's the most clean-cut way of not mixing anonymous and regular files/configurations/whatever.

If my life depended on Tor, I would definitely do this.

[antocv]

Add to that - do not use full web-browsers, but curl/wget/links instead.

[swiley]

This! The fact that a Firefox fork is often used as the "secure for browser" is really pretty disturbing. You have no clue what Firefox is doing 90% of the time and you probably never will.