From a recent wedding:
When the guests arrived at the wedding reception they were treated to the buffet of food and drinks. This is standard - keeps them occupied and happy while you are finishing up pictures! When the couple arrived on scene, they immediately cut the cake. By this time the guests were ready for dessert, so it worked out nicely.
(HERE IS THE TIP!!!!)
The great thing was that as soon as they cut the cake for photos and video, the servers brought out already cut slices and handed them out to people, while another two servers starting cutting the actual cake. It helped for there not to be a line of people waiting for wedding cake! Brilliant! This is especially helpful if you are having a shorter wedding reception.