1. Say no to cake-cutting fees. Some caterers will charge you extra to cut your wedding cake. In some cases this fee is to encourage you (that's putting it nicely) to go with their cake, which doesn't carry a cutting fee. In other cases, it's just a way to charge you more. Yes, it takes time and effort from servers plus extra dishes and extra dish washing to serve cake. But not all caterers will charge you for this additional service, so why not go with one who does it for free?
2. Cork the champagne-pouring fees. Equally avoidable are champagne-pouring fees, which seem especially egregious since they only require one extra glass (that you've probably already paid a rental fee for) and a few extra minutes of servers' time.
3. Keep the cocktail hour food simple. It's true that tray-passed hors d'oeuvres can be less expensive because the servers are effectively limiting how much food each guest can eat by offering only one piece at a time. However, it takes effort to prepare hot appetizers and servers to pass them around. For less-expensive options, think cold appetizers like raw fruits and vegetables and cheese and crackers. Some caterers offer these for a very reasonable price; if yours doesn't, look into purchasing platters from a grocery store or putting them together yourself.
4. Do it buffet-style. Buffets can be less expensive because they require fewer servers. Even a manned buffet may only require two servers to portion entrees; the guests can serve themselves the side dishes. A few additional servers can circulate the dining room, pouring drinks and clearing dishes. Compare this to the number of servers required to bring everyone multiple courses at the same time and clear plates between each course. And many guests actually prefer a buffet over a seated dinner because it gives them more options and lets them choose what they are hungry for at the moment instead of having to choose months in advance.
5. Choose pasta or barbecue. These are two good options for feeding the masses inexpensively. The down side is that, well, most people know that these are inexpensive options, and especially if your guests are coming in from out of town, you want to treat them right. But if the food is delicious, they probably won't care. Wouldn't you rather be full on cornbread and brisket than craving McDonald's after eating a 4-ounce beef Wellington with a side of sautéed spinach?
6. Use disposableware. Using paper and plastic instead of renting china and silver can cut your costs. It isn't as elegant, of course, and sometimes it just won't do, but you might be surprised by how nice looking some disposableware is. Just make sure you can see what you'll be using before you agree to it. Also, know that you may be able to rent low-end "real" plates for the same price or even for less than purchasing fancy disposableware (which can cost $1 per item—that adds up fast).
7. Don't hire servers. This is an extreme measure that will only work for casual weddings, but if you can get by without servers, you'll save big. Many restaurants and caterers offer what is called "drop-off service," where they will prepare the food at their location and then drop it off hot at your wedding in disposable trays. Your guests will have to serve themselves, and your friends or family will have to clean up, so this option is probably only viable for a casual wedding, but you will save hundreds of dollars.
8. Provide your own soda. A caterer may charge $1.25 per person for all-you-can-drink sodas. This price might sound like a good deal, but think about it. Not all guests will drink sodas, and how many sodas will the average guest who does drink a soda consume during a six-hour reception? Will your 100 guests consume $125 worth of soda? If you bought your own soda on sale at $2.50 for a 12-pack, you could buy 600, 12-ounce cans of soda for $125. Your 100 guests aren't going to drink 6 sodas each. Buy 25 cases of soda, spend $62.50, and you'll probably have extras that you can drink yourself later. You can also probably offer a wider variety of options than the caterer would, if you wish.
9. Provide your own alcohol. You know how when you go to a restaurant you'll pay $7 for a glass of wine when you could buy the whole bottle of the exact same wine at the store for the same price? By working with a caterer who allows you to provide your own alcohol, you'll not only avoid paying a markup, you'll also be able to choose any price point that works for you—even wine that costs $2 a bottle. You can also choose whatever brands and flavors you want. Why pay $700 for 100 glasses of wine when you could pay as little as $34 (6 glasses per bottle, 17 bottles at $2 each)?
Don't feel pressured to do your catering a certain way because of what you've experienced at other people's weddings or because a relative or caterer tells you "that's how it's done." Remember that you're really just buying dinner and drinks for a whole lot of your friends and family. Think about what they will enjoy, what will suit the tone of your reception, and what price per person seems reasonable to you. Then you'll be able to choose the best and most affordable catering option for your wedding reception.