What is the best way to improve visualization? Visualization (seeing a chessboard, where the pieces are and how they can move moves ahead in your mind) is an important part of tactics and calculation. 

What is the best way (or a good way) to improve it, I mean for beginners?
In my experience at first you should just work on chess as much as you can, especially on combinations. If you get comfortable with visualizing positions that result from the combinations you will notice to be able to also follow positions in chess books. 
Then it's time to read endgame books. At first you will not be able to follow the moves too deep, but since the positions are simple you will be able to follow it for a while, that's useful for your endgame, and soon you will notice that it's getting easier to follow even deep lines.