The Win, Draw, Loss method is very simple and takes into account the proportion of past wins, draws, and losses over a specified period of time. By calculating the number of wins, draws and losses for both the home and away sides and then combining them it is possible to produce a statistical probability of the possible outcome of the game.

As an example this is roughly how Betchair.co.uk handles this method,

1. For a specified period of time the number of wins, losses, and draws are counted for each side.
2. The percentage probabilities for home wins, draws, and away wins are then made. For example, the home win percentage is calculated as follows:
   (( HW + AL) * 100) / total number of matches
   Where,
   HW = number of home wins by home team
   AL = number of away losses by away team

Once you have a percentage probability for each outcome a decision can be made on the most likely outcome.