Many favorites are over-bet, even on a betting exchange. Always read the grey market text and rules and regs when betting. Always look at prices you wouldn’t like to be on before you look at prices you do want to be on. Choose an involatile market for your first bets; for example, total goals in a football match, bowlers’ wickets in a Test match or indeed total tries in a rugby game.
Have a small bet on a few games of your choice and see how you get on. Worst case scenario, a £2 play in any of these markets should not cost you much. Do your research. With the internet and the endless written material available to all it is very easy to make some statistical based assumptions about a game. For example, if you are playing the time of the first goal in a game between Manchester United and Arsenal, your research might indicate that the first goal in the game over the last ten years on average comes in the fiftieth minute of the match.
The spread betting price will be around 37–40, and therefore you would surmise a buy is appropriate. This can be done for pretty much any market and then you can ascertain if your gut feeling is right.