In order to make long term profits you must be making value bets. Putting it simply the
odds you receive from the bookmaker must be greater than the true odds of your horse
winning the race.

Imagine betting with a friend on the outcome of tossing a coin. The true odds for say
heads is evens or 1/1 . Lets assume you bet on heads at evens i.e. for every head that
occurs you win £1 and for every tails you loose £1. After a large number of tosses you
and your friend should both have won and lost the same amount because you were betting at
true odds.

Now imagine you can convince your friend that for every head that turns up he pays you
£1.25 and for every tail you give him £1. This now becomes a "value" bet. Sure
you may loose the first five tosses. However over a long period of time statistics dictate
that you will win a lot more than you loose. This is because you are receiving the value
odds of 5/4 when the true odds are evens.

With games such as roulette it is mathematically impossible to ever
achieve a value bet. With horse racing however if you are prepared
to wait for the right opportunities, there will be horses whose
chances of winning are far greater than their available odds would
suggest. There are many reasons for this. It could be that the horse
has been laid out by the stable to land a gamble or perhaps its
true form is a lot better than it showed on previous outings. Perhaps
it is running against a highly fancied favorite that has been recommended
by all the papers but who in reality is not in form.

If you can identify such horses consistently you will make long term betting profits.