The Basics

String Shortening
One of the common mistakes that people make when they're starting 3A is to use full length string. However, due to the fact that you're essentially playing with twice as much, taking the extra couple inches off is a huge amount of help. I shorten to my belt, but you should really play around with some different lengths to see what works.
Learn Weak Hand Tricks
For most people, the hardest part of learning 3A is taming their weak hand. You can speed the process up quite a bit by learning some tricks you already know with your opposite hand – your brain already knows them, so they come a lot quicker than they did the first time, and it helps your subconscious figure out tilt direction. It also fixes your throw.