An axe spins at a fixed rate determine by the length of the handle. Thus, the axe sticks at certain fixed distances, i.e. after one rotation, two rotations and so on. Traditional tomahawks have standardised around 18" long. Modern 'tactical' tomahawks are shorter, around 15" long.
For a trad hawk start at five paces. Adjust half a pace forward or back depending how the hawk lands. You dont have to throw very hard but you do have to be positive about releasing the handle or you can pull the axe low into the ground.
A straight handle with no end flare or other grip features is best to get a clean release. A simple slide-up head design means the handle can be replaced easily if/when it gets damaged. You can throw any regular axe but the grip might be too 'grippy' and the handle wont be as easy to replace, and if it is not the standard length you would have to find the right distance for it.
This is the video I'm basing my throwing on:
http://www.youtube.com/watch?v=hLT4tSLU9G0