Here are some links to look at

Here are my notes from the downwind chalk talk
University of Hawaii sailing tips
Sailing world link page Lots of great links!
420 Tuning guide!!! and another one
Suunto sailing tips
Another article for tuning your boat in general for different points of sail
Team Vanguard Club 420 site
University of Washington sailing tips
Pinnell & Bax racing tips
Beginner racing tips, don't think yur too good for this