I've picked up a lot of tips on handling from the forum, as well as Mike Birner's free sessions at the beginning of the year. I won't blame any of the following on them, but I thought I'd post my current understanding here for further comment and/or (especially) correction:
Descending off camber to turn back across face of hill – weight on outside pedal; weight towards front tire (better to have rear tire slip around than have front tire give way); I find this hard to do, but when I get it right, man it works
Riding through mud – do not hesitate pedaling when hitting mud, if anything gear up and keep going; sitting, weight towards rear, let front find it’s way/light grip on bars; if you're gonna run it, well run it
Up hill – weight back far enough to prevent wheel slippage, but beware of pulling up on handle bars lest one pop a wheelie
Moderate descents – even weight distribution; out of saddle a bit, like riding a horse
Sharp descents – weight back; out of saddle to smooth out shock of flattening out
Tire pressure - seem like low is good (30-35psi) unless you are on a dry, flat, relatively smooth course, then splurge on 40-45psi.