Use a website that includes the TS, or topspeed ratings; such as https://www.racingpost.com/
Go through each race card for the day and follow the steps:
STEP 1
Go through and note all horses that are running who have been placed in each of their last three races.
STEP 2
Eliminate all horses that are not rated in the topspeed ratings.
STEP 3
Eliminate all horses that are not forecast favourite or favourite
STEP 4
If two horses are quoted at the same forecast starting price then both horses are to be backed.
IF no horses are found then:-
STEP 5
All the horses that qualified through topspeed ratings will requalify.
STEP 6
Eliminate all horses who are not quoted second favourite in the SP forecast.
Then bet accordingly, using dutching or flat stake.
If no horses qualify under both rules then there is no bet for that day.
What you are backing is horse(s) who has shown consistent form and returned good times. So the horse when running against others must have a good probability of win or place.