Although I mainly like to make my own luck through form study, I always have one system I've worked out going for interest sake.

I used this one over a couple of years and I did very well from it, but I have simplified it because a couple of rules weren't helping it. I like it because it is quick and easy. Resurrected it for last Saturday and it did fine. Win bet only:

1. Sat. Metro Adl. Syd. Brisb. No Hurdles, Maidens or 2yr. old races.
2.Add placings last 4 starts. Total must be no more than 9 [0 or S =10] Ed: I use this rule in a lot of my systems as it guarantees decent form and fitness.
3. Last start must have been 21 days or less
4. Track no worse than dead.
5. Max weight 57kg after any apprentice allowances.
6. Morning line odds no more than $7 from:
http://www.tabform.thewest.com.au/j.../TFFrameset.jsp
or choose your own source.

Saturday 27th. Selections:

Melb. Slow track so no bets.
Syd. R1/1 Mamma Lamia.
Adl. R3/2 Coolgardie [Win $3.60]. R5/4 Mandezvous.
Brisb. R3/2 Umaprience [Win $3.70]. R6/1 Tycoon Rose.

Bet 5 units. Return 7.3 units. A reasonable result.

Naturally better odds could be found as these are just from the above site.