don't sit down, in almost all dirt situations you're better off standing up.
keep your weight towards the rear except those berms you're seeing, slide forward on the seat (this is where you'll want to be sitting down) stick out your inside foot, weight the outside peg (squeezing the tank with that knee) get the back tire loose and stay on the gas, once the bike is pointed in the right direction you want to get weight back on the rear the resulting increae in traction will get you moving forwards again.
The best thing you can do is practice, you nee some T.I.T.S. Time In The Saddle!!!
Know that you are GOING to drop it, it's OK, it's part of dirt riding.
Try to stay loose, tension on the dirt is bad just as it is on the street.
Most of all have fun, learn to ENJOY the feeling of the back end getting loose ( I enjoy it on the street with the Bandit!)
I grew up riding in the dirt, if there were more good dirty riding spots around here I could live without riding on the street at all.
SOTGMOTT Some Of The Gear Most
Of The Time