No clever solutions here -- you just have to grind this out. Every board is random and unique, so here are a few general strategies:
Start by focusing on the middle of the board and clearing as much real estate as possible. When you get stuck, move to the edges of the board, as they will often help you "walk" along the edge and you will clear a lot of previously difficult sections. However, it is pretty common to get some "coin flip" sections of the board where you simply have to guess, especially when you're down to a small number of remaining flags.
My stats are in the ballpark of 35 wins and 500 losses, so expect to lose 10-15 rounds for every win. Some will be in the first few moves, but some will be very late in the round.
You can track your progress in the "My Stats" section.