Instructions
Play "Minesweeper" on the "Beginner" setting until you've gotten the hang of the game and fully understand the rules. When you're certain a square has a mine under it, right-click it to mark the square with a flag so you know not to detonate the mine.
Think about each move before you make it, taking the time to figure out if a square has a mine under it through deductive reasoning. While speed plays into your score, don't worry about that for now.
Pay attention to the logic behind the game. If you're certain a square has a mine under it and the tiles around it all have "1" on them, you know all other tiles connected to that one are free, since you already know where the mine is that is touching that number.
Figure out corners first. If a "1" tile is touching only one uncovered tile, you know it's a bomb. Once you figure out where a bomb is, it becomes easier to determine whether adjacent squares have bombs.
Keep practicing until you consistently beat "Beginner" mode in under a minute every time. Go to "Game," "Options" and select "Intermediate." Take what you've learned on "Beginner" and apply it to the larger boards in "Intermediate." Once you're satisfied with your "Intermediate" finishing time, move up to "Advanced," the hardest mode available.