Most people have trouble with YOs because it's too easy and so it seems wrong
. All you're doing is bringing the yarn over the needle, and making a stitch. Oh, but you say, that doesn't make sense, nothing is anchoring that stitch, it will just be a hole. Exactly! That's the whole point-- it creates a hole and therefore, visual interest. If you look at a pattern with YOs in it, there will be some sort of non-straight-stockinette-stitch quality in the design-- lace or scallops or whatever. The video here on knittinghelp shows how to do it.