If you like Speed Ratings - Andrew Beyer is the authority there.
He does point out though that his use of speed ratings have not been as successful on turf as dirt. Still, he has a few good books which can be ordered thru major book stores in Australia.

Also try Don Scott - Winning in the 90's. Haven't read it, but most readers recommend it highly. Its about $100 though and hard to get - out of print.

Other than that, keep Sunday's results each week as well as a good form guide from Friday/Sat and sit down and look at the winners. You see some patterns emerging after a while which will help you design your own winning system.