Here comes my value-strategy:

Use a good source which shows you the probabilities (percentage-distribution)
of results on the basis of good statistics.

It's not easy to find such a good source - an example would be:
http://invarius.ivnet.ru/soccer/champ/champ.htm
(from Russia and partly Russian, but still usable)

Then you take the current odds of your favourite bookie
(that's the one where you have got the most money in the
betting account )

Then you have to compare the statistical percentages
with the current odds.
Decimal odds can be simply converted into percentages by
dividing 1 by the odds (e.g. 1 / 1.5 = 0.666 = 67%)

Example:
Arsenal Chelsea 27 39 34
Odds on Chelsea at e.g. Betfair are 2.40
1 / 2.40 = 0.416 --> meaning 42%
Gives you a difference of 42% - 34% = 8%

Then you can stake those 8% according to the Kelly-strategy.
Stake according to Kelly amounts to:
budget (e.g. £500) multiplied by 1/10th of the
valuation (here 8% thus 0.08) divided by the
decimal odds minus 1 (here 2.40 - 1 = 1.40)


Thus, at our match 40 divided by 1.40 = a £28.57 stake

The Kelly-strategy has the advantage that the stake
is calculated on the basis of probabilities and your currently available
budget.

For more info go here