When we say "I DO", we want the magic of the day to stay with us for years to come, especially the memories. That is usually why most couples will pay big bucks for their wedding photographer. Instead of having a firend of the family take the pictures, they will usually go for professional photographers.
But although he is a professional, I would strongly recommend that you sit down with him before the big day to set up a list of shots that you absolutely want. Usually, the bride will want to have picture of in her wedding dress with her new husband alone. Some couple will ask to see not only the inside of the wedding chapel but also the outside.
What about your wedding cake? Do you want to have a shot of it?
By giving your wedding photographer ideas of what you would want, remember to leave him enough freedom to also get you those shots that you would not have thought of : throwing of the bouquet, the old uncles dancing, etc...
But above all, remember to have fun on your wedding day, it is after all YOUR day!