What are the best practices for writing maintainable CSS?

Question

I am just starting to explore this area and wonder what are the best practices when it comes to production of clean, well-structured and maintainable CSSes.

There seems

Answer 1

I like Stefano Mazzocchi's suggestions in the post titled Why Programmers Suck at CSS Design. Among other things, he explains how to start from a clean slate, whether to use em or px, how to define fonts, etc. I would not use all suggestions (e.g. I would be hesitant to import any CSS -- or any other -- files from Yahoo!), but some ideas are pretty good.

And a few more suggestions: 100 Exceedingly Useful CSS Tips and Tricks