Mine is a little hard to explain in one post all horses start with a rating of 120 and these are the catg i use

Win%
Place%
Average Prize Money

these are ranked in oder and the top selection in each gets 1 and so on down the list

then i take these amounts away from 120 so if we have a horse that is the top selection in these three catg it would be 120-3


Then i ad the beaten margins of the last two runs to a maximum of 10 lenghts in each....this is then deducted from the 120then i use the track and distance win and place percentages in the same maner and this is all deducted from the 120 so in all i use 9 different bits of information to get my rating....i use an excel sheet i wrote up and it takes me about 2 minutes to collect the form then work out the top raters.