Here's food for thought, given the bias towards longshots being way overpriced on Betfair, I've always lived by this saying in punting terms, as it's proven in the data.
"The worse a horse is, the more you'll lose laying it, unless you can find a way to lay it lower."
Think about the words contained in that saying, it summarizes why people lose money, the thought process is a punting thought process and not a laying thought process, the very first danger to the novice layer.
Imagine a rails bookmaker offering $5.00 about a $3.50 shot or $1000 about a $150.00 shot, then think about how much they make, 15% to 20% less turnover tax and track fees and licences.
And people want to lay horses higher? Madness
If bookies gave Betfair prices about horses, there would be no bookies within a month or less, and that is why layers have to lay smart and not take what is offered just because they think it won't win.
If I lay this horse at this price and it wins at the expected ratio, will I make a profit - unfortunately the answer is usually no, especially when commission is factored in.
I posted this before, but favourites at Canterbury are overbet and so are first starters, you can make a profit laying at betfair prices plus commission, and there are plenty of other angles also. There are many more thatwill bust you at Betfair prices though. You must research before putting hard earned on or guessing or picking.