Consider your child's temperament when planning the celebrations. Some children are shy and retiring and their idea of fun does not include having a huge party and having to deal with so many people at the same time. If you have a child who prefers small intimate gatherings, you can make the day special for her by involving her in the preparations. May be she can help butter the sandwiches or blow the balloons. Keep the number of guests to a manageable figure so that you have time to pay attention to your child and make him feel special instead of spending all your time running around playing the good host.
Presents are often a bone of contention.
Your child is bound to want to rip them open as soon as he can get his hands on them. Remind him that if he opens his presents before the other children have gone, he is probably going to have to share them with the others. And if he doesn't want to do that, he has to be prepared to wait. If your child misbehaves or exhibits bad manners during the party, do not yell at him in front of the other guests and humiliate him. Take him aside for a quiet word in his ear.