How do you straighten the shaft of a billiard cue?

One method - fasten the shaft to a straight pole. It should follow a new shape now.(the pole). Apply moisture and hair dryer as often as possible. In a weeks time, depending on the humidity of the country your in, it should keep the cuestick straight.

You can also add a SMALL amount of vinegar to the water to help the wood become flexible (until dried). Vinegar can discolor the cue though, and you may have to remove some of the finish to get the moisture into the wood of the shaft.

Second method - Hang the cue - hangers can be purchased or made using string and rubber bands - a hanging cue will be straighter than one against a pole because the shaft has a taper (cue shafts do not have a straight side). Use the moisture as described above.