I'm afraid it look's a bit simple, but it has been quite profitable for me. As mentioned it's an under/over strategy and it's based only on statistics.
Let's imagine that there's a match between team A and team B. (A is the home team). First of all I will check what is team A's average of goals scored and conceded at home. Let's say that team A scores 2.1 and concedes 1.20 - total of 3.30 goals average in team A's home games.
Then I will check what team B's average of goals scored and conceived in their away games is. Let's say that team B scores 1.75 avg. and concedes 1.15 - a total of 2.90 goals avg. in team B's away games.
Then I take the two smallest numbers 1.15 + 1.20 = 2.35 - minimum goals in this match. In the same manner you find the maximum which is 3.85. The avg. of the min/max is 3.10 which is much more the line of 2.50, so I will bet over in this game.
If I get an avg. of 2.70 or more I will bet over with high stakes. If it's between 2.50 and 2.70 I will decide by myself if the OVER bet is worth a try, but it will definitely be with small stakes. If I get an average between 2.30 and 2.50 I will decide if the UNDER bet is worth a try and it will definitely be with small stakes.
If I get an average of 2.30 or lower I will bet under with high stakes.
Of course, sometimes I don't necessarily bet on the 2.50 line. I might also bet on lines of 3.00, 2.00 and others.
I have already increased my bank by 50% in one month using this betting strategy and I will certainly continue increasing my betting bank further.