Stack: Zradix gives a good description of what to look for. Doesn't make much difference if your taper is a little short, but it should fit snug without wobble when you push it in the point. If not, one of about three things is happening. The taper isn't being cut true. That can be a problem with pencil sharpener type sharpeners. Two, there may be some glue or other obstruction inside the point. Or three, you may be putting too much glue on the shaft and it's hardening up before you get it seated properly. Of course, if it wobbles when you try dry fitting a clean shaft into a clean point, then only no. 1 can be the culprit.
Just to clarify, you are talking about the shaft wobbling in the point, correct? not the entire arrow wobbling as you spin it with the point attached. In addition to the factors already mentioned, the latter can be caused by an off-center tip and/or crooked arrow. Keep at it, you'll figure it out.