The best things to consider when choosing a caterer, if you go that route, are - naturally - price and quality of the food, but also how flexible the caterer is willing to be with dietary needs. If price is not an object, always look for the highest recommended caterer in your area. Without good recommendation, it's up in the air whether you're getting a good caterer. You can either get a great caterer, or one that could cause issues (like simply not making good food). My city has a program called the A Lists and a site called Angie's List that provides detailed reviews and recommendations for trades and services. If you have something similar in your area, that's a great place to start. On the low end, caterers usually start from $10 a plate and require a minimum count. Expect to spend at least $1000 on just food when going this route. When researching venues, also see if they provide food. Some venues require that you use a certain caterer, which will limit you - especially if you don't like the food.
Think outside the box
You can have just about any restaurant cater large events. They'll be cheaper but probably won't provide any servers or even delivery. You'll have to factor that into your budget.
When meeting with a caterer, try to have a taste testing to determine the quality of food; the biggest complaint of wedding food is how dry the chicken is. Because while you won't be able to choose a dish everyone likes, you can choose a cook that will produce tender, juicy meats and savory vegetables. Always try samples before you commit, if you can.