Minesweeper/Game patterns

To become proficient at the game you must learn to recognize patterns in the playing field. In the following text: In the "Given" pictures:
 * x = don't know/don't care
 * w = wall
 * n = any number
 * u = uncleared space

In the "Play" pictures:
 * m = mark as mine (don't clear)
 * c = click to clear (not mine)

Easy patterns:

The simplest kind of pattern is if there is a number, and there is exactly that many number of uncleared squares bordering it. In this case, EVERY uncleared square bordering it must be a mine. Some examples:

Given: 1 n n u Play: 1 n n m

Given: w 2 n w u u Play: w 2 n w m m

Given: n 3 n u u u Play: n 3 n m m m

Other patterns:

Given: n 1 2 n u u u u Play: n 1 2 n c u u m

Impossible patterns:

There are times when it is (provably) impossible to determine which of two uncleared squares is a mine, because either option would produce the same numbers on the board. In this case, you should randomly choose one of them, since you will have to sooner or later, and if you're going to lose, you might as well get it over with quickly. Some examples:

Given: m m m x u 3 x u 1 w w w