The grip is easy. Pick up the cue a few inches from the butt end as if you were going to use it as a club. Relax the tension in your hand. The cue should rest lightly, held just firmly enough to stop it sliding around. You will find that you are holding the cue with the thumb and first two fingers, while it is just resting on the back two fingers.
The grip is so natural that there is only one common fault – gripping too tightly. This cuts down on the freedom of the cue arm, and it also prevents the natural slight squeeze of the fingers as you strike the ball. This little squeeze is automatic if the cue is held lightly to begin with, and it increases the ‘feeling’ of the shot.