Bike setup is easy to overlook, but made a huge difference for me. Ryan Young's DVD starts with bike setup, and I was saying to myself "yeah yeah nothing really radical here" as I was watching that part of the DVD. Shortly after that I attended a 2-day trials-for-newbies school put on by one of the local trials experts. He convinced me to try handlebar and lever positions which he found to work really well over the years. Wow! What a difference! The setup is actually very close to Ryan Young's. The key factors are:
1) Brake and clutch lever position should be almost horizontal, maybe angled down just a little.
2) If you look from the side, handlebar position should be such that crossbrace lines up vertically with bottom part of the bar. This brings your wrists forward and improves ergonomics for the front-wheel-high(er) position, which is more important than front-wheel-low(er) position. This adjustment controls your entire body's CG, so not surprisingly it had the greatest impact for me personally, even on level ground and on cambered turns.
3) Clutch and brake levers are operated with only the index finger. This is your index finger's permanent home. I never take my index fingers off the levers even when I'm riding the loop trail. When you pull the clutch lever and it stops against the other 3 fingers, the clutch should be disengaged, but just barely. So the friction zone starts immediately as the clutch lever comes off the 3 fingers gripping the bar. This not only improves intimate knowledge of the friction zone, but also is much less fatiguing in the long run.
And as others said, steer with your feet. Try riding up and down your street on top of the curb stones. As you get better, try going around the corner on top of the curb.