The best man - How to do it?

I have recently attended my brother's wedding in Europe I wans the best man for the first time in my life..
I have been to many weddings but never as a best man so was a bit scared when I was asked to do it. It sounds like a responsible job and everyone expects you to be on the ball although no one really knows what to do!!!
. Therefore I have decided to do some research on the net to prepare myself for it.
It helped me a lot, however I have made some funny mistakes.