Some things I've noted over the last 5.5 years of learning to ride in the dirt:
-going a bit faster is almost always better than going a bit slower (provided you have the suspension to do so)
-the weight needs to be on the side of the direction you want to go...want to go right, then make sure you are weighting the right peg. I have noted so many crashes (myself and others) that are due to lack of commitment to this...trail goes right, but you climb up to the left and out of the trail because you weight the high side peg rather than the low side.
-the bike goes where the eyes go...fixate on an obstacle that you don't
want to hit, you'll hit it every time. Identify the stuff you want to avoid by identifying the path you want
-stand up more...it gives you more leverage on the bike, and it gives you more "suspension"
-stand up, lean back, and grab another gear and more throttle in the sand
-when it feels like the bike is going down, throttle usually helps stand it back up...moving bikes like to stay upright better than stationary ones
-ride...ride...ride. The best money spent on your bike is in gas