This leapt out at me from my form guide after the Australian Cup yesterday (it seldom happens before so naturally I wasn't 'on').

Basic method =
* horse must be racing in field of 12+ starters
**open age race (no 2yo or 3yo only races)
***barriers 1-4
****must be in top 5 for average prizemoney (available in The Wizard)

Yesterday it got Roman Arch and Malta as sole selections.
I've got no idea how it goes long term but it might be something worth researching if you are enthusiastic. I'm a bit lazy about research these days.

Basically the logic behind each of the bullet points is:
*I'm interested in something I can put on and forget so field size may boost dividend size. Also the greater the field size the greater the disadavantage with a wider barrier .
**Prizemoney averages can be unrealistically high with horses who have only had a few starts.
***Luck in running plays a major part in racing (a bit like the bounce of the ball in footie). One bit of luck in running that you can probably ensure doesn't go against you with this rule is that your horse most likely won't be trapped wide.
****Average prizemoney over a career is one indicator of class.

Weaknesses: the main one is that NZ horses will not be recognised by the average prizemoney rule. Perhaps those of you with a destructive bent can add many more here.