If you're going to be serving food in the "buffet-style" then your food display and layout is one of the most important things to keep guests moving in the buffet line in a steady and streamlined manner. If you take a logical approach and have the right set-up, then the buffet serving style works as it is intended to work--cutting out the middleman between the diner and the food itself.
First Course to Last
For a smaller buffet at a smaller party or event, it is always good to display food from the first course to the last course, in that order. In other words start with the salad or an appetizer, then move on to entrées, following with the side dishes and then finish with the dessert. You can also place dessert on a separate table (so guests aren't having to mix their dessert with their appetizer). For larger buffets at larger parties and events, break up the courses with separate buffets--appetizers and salads in one buffet line, entrées in another, desserts at yet another. This way guests can eat, have their plates cleared and decide what they want for their next course instead of having to try and cut back into the one line serving everything, which causes confusion and disorder.
It is important to have numerous ways for guests to serve themselves for each dish. In other words, a number of tongs in the big bowl of Caesar salad, so that many people can serve themselves at one time. For dishes that are supposed to be kept warm, the food should be kept in a covered serving tray, warmed by a Sterno jar and someone from the catering crew should be there to serve them, so diners are not holding the top of the serving tin and trying to serve themselves at the same time. One person serving everyone also guarantees more equal portions and fewer people touching the food.
Another idea that has been put into practice at many events has been multiple buffet tables that serve small plates of a variety of foods. This way the lines move quickly and people can easily sample a lot of food and come back for seconds or thirds of foods they really like and want to make a meal out of. This is effective for breaking up a party and keeping everything from grinding to a halt as everyone waits in one long line for dinner, hungry and annoyed.