How to force the opponent to take the x squares?
The permutations of the game makes it hard to come up with one specific strategy. Personally I like to "dance around" the X squares, trying to tease my opponent into placing his pieces there. But always remembering that it should cost him more than it should ever cost me.

As a general rule, your objective is to limit the number of liberties (that is, the number of moves) available to your opponent, while at the same time increasing yours. This is what is called the mobility strategy. When this objective is attained, one is said to have control of the game.

However, don't forget that you must force your opponent to make a bad move : it's not enough if he has even one non-disastrous choice at each move ; he must have no good moves at all.