Straddling your legs in the beginning is also a great way to get to know the balance (its how I started them). When you want to progress to legs together you need to start slightly twisting your body so you dont spin around your balance point. Hmmm, I cant explain it well enough so here is a quote from Ido that he posted on my handbalacing log on his forum 
"Ricky, as you close the position, it is usualy helpful to rotate the body sideways more, as if you are externally rotating your humeros in a rotator cuff exercise.
The full closed position is will become much easier if you start to limit yourself to first only balancing with the elbow angle and the wrist moving and the rest of the body locked, and finally only with the wrist.
In the straddled position people are sometimes relying too much on their legs to balance, which makes it difficult to advance to the full elbow lever version.
By the way, this is true to all handbalancing. The end goal is to 'take down the balance' to the wrist only. The rest of the body is locked into position.
Ido."
Basically I would start in as wide a straddle as you can and then once you get that solid start working on half straddle and feet together. If your wrists are bugging you, blocks are a great help for these.
