Here is my system:
Lay correct score 0-0: It rarely happens especially with teams with blasting attacks like Real Madrid, Barcelona, Juventus, Inter, Milan, Arsenal, Man Utd, Chelsea etc.
Those teams rarely finish their games 0-0 irrespective if they draw, lose or win. So I have been looking closely for this kind of bet.
At Betfair you may
1) back 1 or more goals to happen in a game with odds always around 1.05, or
2) lay correct score 0-0 at odds always around 12.
The two above are basically the same. The problem of Option 1 is the little profit that you get, and with option 2 it's the huge liability it incurs if the game would really finish 0-0.
Last week I did some statistics of around 200 matches picked randomly from a scores site, and basically I included all matches (even there where japanese teams etc.). The draw 0-0 only happened 16 times from those 200 games, so a very nice 92% strike rate. I believe that if you are more selective, this may easily go up to 95%-98% When I evaluated the 0-0 scores, most of the 0-0 draws were lower division teams unknown to me.
When I assumed a starting stake of £5 and following a very basic staking plan with lay odds of 11, after 200 matches the betting bank had become £582! What a nice profit.
The problem with this system is that the liabilty is so high if you are unlucky enough to hit a 0-0 game even with high scoring quality teams.
Just last saturday I started this system with real money and bet on Man Utd, Arsenal, Real Madrid, Roma, Barcelona and their games all had a lot of goals, so I won the bet.