Counting the number of stitches varies by region, I think, as I have heard different methods used. The main thing to watch is that all your stitches are the same size! That takes practice.
Your question about the under, or pricked finger is a good one, especailly in the winter when my fngers crack. I catch the under stitches with my thumb, and it gets pretty sore sometimes. The best thing I have found it to use tape on my thumb. I have used Band-aids, white adhesive tape, duct tape, whatever and they all work. There are little plastic patches you can buy to apply just where you need them, but the bandaid stuff works just about as well and is usually available right now! There is a little metal thimble thing I saw in a quilt store that was designed to place on your under finger/thumb, whatever you use. I bought one, but it is so small, I don't know where I put it, so I don't have any first hand experience using it yet! :?
BTW there is a companion pocked metal thing to put on you pusher finger. The under one has a smooth surface. They adhere with sticky tape that is reusable.