Pool cue shafts should be straight to give the player the best performance during games. If the shaft is warped or bent, the pool balls will not roll where the player wants them to. Though preventing the warpage in the first place is preferable to trying to fix it later, there are some methods for straightening pool cues that may work for a while. They include replacing the warped section of a two-piece cue, suspending the cue in a vertical position and bending it with your hands.
Replace the warped section. This will only work on two-piece cues that can be unscrewed. Usually, the bottom section of the cue handle is the piece that is warped. Online shops or your local professional pool and billiard supply shop will have replacement parts available.
Tie a string around the cue near the tip. Tie the other end of the string to something such as a door frame or closet pole that allows you to suspend the cue in a vertical position. Leave the cue hanging there undisturbed for a day or two. It may eventually straighten, especially if the warpage is due to being stored leaning against something instead of lying in a case.
Press the cue back into shape using your hands. It is important to remember that this method may snap the cue stick in two. Do this with extreme care. Determine where the warp occurs on the shaft. Lay the cue on a flat surface and roll it slowly while looking at it from the level of the flat surface. When you see the largest gap between the flat surface and the cue shaft, mark it with a pencil. This is the apex of the warp. Stand the cue against a wall and gently press it with your hand at the pencil mark in the opposite direction of the warp.
Send the warped cue stick to a professional pool and billiard shop for repair.
By far the best way to deal with a warpage in your pool cue is to prevent it in the first place. Store the cue in a flat position, such as in its case, so that leaning it against a rack or a wall will not harm it.
It is very likely that, even if you can straighten the warpage yourself, the cue stick will return to its warped shape because of the nature of wood.