The best way to improve your game is to get all the things right that are required to play the game in a professional way. Until you start playing the game like the professionals you cannot improve your game. You have to think ahead of the shot that you are playing. That is what pros do, they even look at their third or forth next shot.
Practice is the second most important thing to do in order to improve your game but practicing the right way. The first thing that you need to improve is the way you hold the cue. hold it like you are going to hit someone with it. Keep the thumb and index finger firm on the cue and the rest of the fingers a little loose so that when you move your arm three of the fingers are free for the movements and that will give you more control over the cue.
Now the above image shows the styles of different players and how they hold their cues, it all depends on you and how you are comfortable so be always comfortable so that you can concentrate on the pot and not on your discomfort while playing.