At the moment I do all my betting with the TAB's (my current system backs longer odds horses that generally pay better with TAB than bookies). I have accounts with NSW, WA & Qld (most betting is with NSW and WA) and place the bet with the TAB offering the best odds on the horse in question.

I always place my bet within about 20 seconds of the jump and only if the price on TAB exceeds my bet margin by a threshold amount as Debug indicated - you need to vary this threshold a bit depending on the amount in the pool but about 10% of the price is a good guide.