I find that damn tricky too - I reckon most people do. My only suggestions is to watch that you're using all of the front of your foot to stand on, not just the balls of your feet; i.e. make sure your feet aren't rolling forwards, if you see what I mean.
Oddly (and I know you're not supposed to do this) I find that resting the heel of my front foot against my back foot helps enormously (i.e. like standing on my back foot). I think it's a sort of illusion, but it feels like I'm propped up, & I stay much more steady.
A. [/i]