If you are going to shorten a golf club, there are a few things to keep in mind. The more shaft you cut off, the lighter, more stiff, and effectively flatter the club becomes. For every 1/2 inch you remove, you will lose approximately three swingweight points. You can readjust the swingweight by adding lead tape to the head of the club. Any amount of cutting will slightly stiffen the club. It will probably go unnoticed if you take 1 inch or less off the club. Taking 2 inches off will change the flex of the club. If you are shortening irons, every 1 inch you shorten the club will make the iron effectively play 2 degrees flatter. You may need to have the lie angles readjusted after shortening them.
Remove the grip using a utility knife with a hook blade. Remove the grip tape from the shaft.
Measure the amount of shaft you want to remove (add an additional 1/8 inch to make up for the end of the grip), and mark the spot with permanent marker. If it is a graphite shaft, wrap two layers of masking tape around the cut location. This will allow the marker to be visible yet will prevent the graphite from splintering while being cut. You don't need to use masking tape for steel shafts.
Align your cut mark with the blade of the saw and secure the club in the vise. Put your safety goggles on and hold the club so it will not fall as you cut.
Turn the saw on. Slowly and smoothly, cut all the way through the shaft. Try to cut it all the way through in one motion, otherwise you may get an uneven cut. Turn off the saw and unplug it before removing the club.
Use sandpaper to smooth the rough edges of the butt end of the club. Put a new grip on the end of the shaft to finish the job.