There is a slight variation on track stands that is used in trials. It is different from the rock back and forth used on a fixed gear bike, since you don't have a fixed cog. You turn the wheel about 45 degrees and lock the front wheel using the brake. You maintain you balance by applying pressure to the bars in one direction or the other. There is a sweet spot angle for the front wheel where the bike becomes stable.

Hard to explain, but might be worth a try. Center the bike in a hallway, turn the handlebars (45 degrees) and hold yourself up using your outspread elbows. Try to balance, and if you start to fall, just touch the wall with you elbow and recover. This exercise will teach a lot about your balance point, your position on the bike and how subtle your corrections need to be.