Preparation
1. Get the right tyres, Michellin Deserts if you can.
2. Get your tyre pressure as low as you can.
3. Keep weight to a minimum.
4. Keep weight to the rear
Riding technique
1. Riding slow in sand is very difficult, speed and momentum are your friends.
2. If in doubt, burn it out. Often, a low speed wobble can be corrected by ample use of the throttle.
3. Stand on balls of feet, elbows as vertical as possible, all the usual dirt bike riding techniques.
4. Practice until you're used to it.
Number 4 is probably the most important, it takes practice to get used to the feeling of the front wheel digging in, and then more practice to get used to rolling on the throttle to bring the front wheel up again. It's good fun when you get the hang of it though.
some photos from our trip across Aussie, plenty of sand over there: