Follow!
http://www.dfn.com/agservices/plugchop.html Follow it 100% step by step or don't bother.
Couple pics from days gone by.....
One on the right is what you want.
I haven't done a chop for years, when you can do it by seat of the pants, feel and knowledge, its better and faster and you don't waist plugs and time.
YOU CAN DO IT!!!!