I had this very same problem. It took me quite a bit of time and persistence to sort, as well as a lot of pain in my shoulders!
My training partner is very good as these, and is very keen to do them two times a week - with the back workout and the shoulder workout. Admitedly if I was training alone I probably would have given up on them when I realised that I couldn't do even one!
I started off not being able to do any whatsoever, so he would help lift me. This was probably as difficult for him as it was me!
However we persisted and slowly but surely the help he needed to give me became less and less. After a couple of months I started to be able to 3 or 4 reps by myself, then he would help me up to 10.
Now we do 3 sets of ten behind the neck and 3 sets of ten in front, twice a week. They are a fantastic way of building up natural size and strength, so I would urge you to be persistent like I was. I still remember how much they used to hurt me, but the pain was worth it!
So if you have a training partner, get them to help you - and persist for a couple of months - its takes time, but then all of a sudden you realise that you can do them - and its an amazing feeling! Isn't this what its all about - pushing our bodies to new places with determination and persistence?!