Read Peter Mays books!
I recently finished Peter Mays book In Search of the Winning System where he accounts his personal journey to devise systems that win money from betting on horses. And I dare say that it is one of the best books I have read on the subject so far. Especially if combined with his other book Forecasting Methods For Horseracing.
Of these two, Forecasting Methods is the more theoretical book which covers the ways of devising betting systems from more mechanical angle and Search looks at systems more from point of view of possible angles that could be used as basis for a system. Of course there is a lot of anecdotal content in Search and I think back cover blurb from Amazon describes it well enough.
Charts Dr Peter May’s obsession with betting on horseracing. In this book the author of the acclaimed Forecasting Methods For Horseracing presents the story of his search for profitable methods, the mistakes he has made, the valuable lessons he has learned and the knowledge he has gained from like-minded racing enthusiasts who have contributed to his 40-year betting apprenticeship. Add to that a range of amusing anecdotes, a detailed analysis of the key race types, and a list of the betting systems he currently employs and you have a book that will make you smile, make you think and probably make you money.
Without repeating myself too much, both books are well worth a read and I don’t think I can recommend them enough. Go read them. You can also download two of his earlier books for free from here. I haven’t read them yet myself, if you have, please let me know in comments.