Best sites i have seen are flyingcirkus 3D univesity, Blaine Austin and Downonthedeck. nothing beats practice. A good set up also helps with flying 3D. If a plane is not set up correctly, it will be very difficult to 3D. Look at the set up tips on this site, they are very helpfull. There have also been some set up tips in 3-D Flyer magazine, by Chip Hyde, George Hicks and many others tha have been of great help, mostly in finding a good CG position, thrust lines and radio setup: Expo, mixing etc.

Gus155
Pro Bro#1949