I don't know if you're going to get any joy on this one mate. You've asked such a general question on such a big subject it's like saying I've got a Sportsman, how do I know which horses are going to win.
The fields you've layed out seem pretty sound (might add track condition) but try to be more specific with what approach you're going to use to get some results out.
Anyway, that's just my impression as a general database sort of guy with no specific knowledge of the one your using.

KV