This is a system I have used for many years, I rarely have a losing weekend and my system can pick out some pretty good roughies.I use Best Bets to work this out with.

My system comes in 2 parts,
Part 1.
I give every type of race a rating

RACE RATINGS
G1 1
G2 2
G3 3
WFA 4
HCP 5
LR 6
C6 7
C5 8
C4 9
C3 10
C2 11
C1 12
MDN 13

Any race not included comes under handicap

I then add up the last 3 finishing positions for each horse in the race and this gives me the favourite for the race.
Example; Horse 1 4th in mdn,2nd in mdn,1st in mdn gives a score of 43
Horse 2 1st in G1,1st in G1,1st in G1 gives a score of 6

Part 2
From part 1 I then use this system to sort my best picks for the day
G: SELECTED HORSES THAT HAVE HAD ATLEAST 1 GROUP RACE IN ITS LAST 3 STARTS
W: SELECTED HORSES WHO WON ITS LAST START
T: FINISHED TOP 3 IN ATLEAST 1 OF LAST 3 STARTS
D: RACED AT THIS DISTANCE IN ATLEAST 1 OF LAST 3 STARTS(50m either side)
J: FINISHED TOP 3 WITH THIS JOCKEY IN ATLEAST 1 OF 3 STARTS

I get these choices based on averages, horses who ran the distance win 52% of the time, with the jockey 35% of the time etc.
G 14.70
W 29.41
T 23.52
D 52.94
J 35.29

1st up and horses with less than 3 starts are excluded.

So my top picks come from this system in this order DJWTG work down from there. I get an average place rate of 72%
I think I have explained this adequately, any questions.