I would say that it's almost impossible to get rid of all stress at exam time. After all it is quite natural to be anxious about doing well - a lot depends on results nowadays - well to be honest it's always been like that - it's not just nowadays!
My mantra has been for years, "To fail to prepare is to prepare to fail"
No use going in to your exam when you've not studied or prepared. Some people leave it to the last minute and cram like mad for a week or so. I believe it works for some - but not for many. All the hard work should be done in the months leading up to the exam.
I read a great exam/test tip once and have used it often. When you learn something new - while it is still fresh in your mind - go and tell someone else about it. Teach it to them, and it's established in your mind. Recalling it is a breeze in the exam. It helps beat the stress!