Have a look at Scott's blog here
http://www.sportismadeforbetting.com/p/ ... ategy.html
That may point you in the right direction. It's a case of profiling the race and laying at odds that have a chance of getting matched.
Statistics are you friend here. rather than buying Betfair data you would be better off buying a subscription for Proform. They are without doubt the leaders in this sort of data.
Try profiling tracks. i.e Lingfield "the longest final furlong in racing". meaning lots of short prices in running get turned over.
There is no easy way here. It's lots of time consuming work & trial and error. What you will find is there is no "one size fits all" strategy. You really have to be selective.