Improving Visualization

Basically this is very simple. In order to be able to read more, you have to read. Read far. Read allot. Read read read. I especially recommend tsumego. But you can also improve your reading in the middle of a game. Just pick a random point on the board and 'see' in your mind the consequences of it. Our minds like to make sense of things so you won't be as focused if you try practicing visualizing random sequences of moves with no goals or objectives in mind. This is why tsumego have a goal. Even if the goal isn't written and you have to decide what it is for yourself, there is at least possibility to live or kill in a tsumego. You could just visualize random problems but that isn't as engaging. In other words, tsumego have goals to make them more fun. So to practice your visualization just read out patterns with goals in mind.