Rule 1: Operate on handicap races only (both flat races and jumps races can be bet).
Rule 2: Consider only horses who finished fourth in its last start.
Rule 3: Must have won at least once in its last six starts.
Rule 4: If more than two qualifiers, then pass the race.
Rule 5: If two qualifiers, then split the stake and back both.
Rule 6: All bets are each-way.

Don't be put off by the simplistic nature of this method; you won't win every time but you will find yourself in front in the long run.