scrap the trots thing thats to hit and miss
but whilst on the lay subject here is ..and i think it is a reasonablly good thing
i use racing odds coz the print is easy to read at a glance
1/ there must be at least 2 openers at odds of 4 or less
2/your lay will be the nag with the most runs at the track
3/must be more than 1 run at the track