Here's a good article on using GMail from Boxes and Arrows.

One interesting thing in GMail is the SLAT principle - Star it, Label it, Archive it, Trash it. This is very similar to the advice from a 'personal productivity' book that I bought earlier this year Getting Things Done, by David Allen. Part of the advice from that book dealt with the day-to-day process of managing and organizing email.

Something else I noticed is the threading that GMail does. This is similar how the latest version of Outlook automatically organizes message. I really enjoy it and believe it helps keep my mail organized at work.