Anybody shorten zippers. I can get a great buy on zippers if I can shorten them when I need one. Ten cent a zipper. What is the best way to shorten them.

Hand stitch a bar tack across where you want the zipper to end. Then cut off an inch or so below the bar tack.

That is the way I do it also. Too risky to shorten from the top as you could lose your pull.

just sew across the bottom to the length you want and then cut it off it will be fine

Ditto on the stitching across the bottom. If they have metal teeth you can take needle nose pliers and remove the extra teeth and that makes it softer on the cut end. With the plastic teeth you just leave them. Cut about an inch below where you stitch. I used to do this all the time (worked in a dry cleaners while in college)