Once you accept the challange of planning your own wedding/event, there are a few bits of knowledge that you should arm yourself with:
First, DON'T ASSUME ANYTHING! 
1. So, one of your girlfriend's, that loves to bake and is usually pretty good, has offered to make your wedding cake as a gift. WOW, what a great way to save and to ensure that the cake is going to pleasing to the palette ~ a win-win situation, right? Well almost right, don't assume that because the cake is edible and the caterers are handling the food, that automatically makes them responsible for cutting & serving the cake. Now, most catering companies are more than glad to assist you with this detail but there is normally a cake cutting fee and the Day-Of is not the time to discover this information.
2. Candy & Dessert Bars are a BIG thing now; heck, I'm having one at the babyshower.... You come across lots of decadent edibles to display and are sure that it's going to win the crowd over. Before we get to the visual, there is usually the task of setting up the bar; have you informed your Day-Of-Manager of your intent and has she/he agreed to take on that responsibility or have you mentioned this to the caterer and she/he agreed to this task? This may seem like a small detail but on your event day, when schedules have been composed in advance and every second counts, this one mission can throw a huge curveball in the set-up process. The display should not only be pleasing to the eye but how the desserts should be cared for, will determine how far off of schedule it puts your vendor.