Great questions! I intend to listen in here because I'm a roadie who has recently switched to mountain biking for at least some of my riding and I'm still pretty pathetic at this, quite distinct, sport.
If I may, I'd like to add a question: how do you keep the front end of the bike from floating up on steep climbs? I'm very fit and climbs in and of themselves are not an issue for me; but the technique on a MTB certainly is! It seems that no matter how much I try to move forward to weight the front end I can't seem to keep it from rising up.
I've found that where I've tackled really technical trails I've had to back off a bit and go in search of trails that were a bit more sensible for me at this point.