Charcoal grills run in a wide variety of sizes. You can get large drum grills with 1400 square inch cooking surface, or a portable table top model that are perfect for a pair of steaks, but not mush else. Similarly you need to determine the kind of cooking you want to do. do you want to be able to indirectly grill whole chickens, roasts or racks of ribs. For indirect grilling you need plenty of space to build a fire on one side and still have room for the food. If you want to make beer can chicken you have to have the lid height to stand up a chicken.
One other thing to look for is airflow control. To be able to hold a set temperature the grill needs to be able to be closed up tight so that the vents are the only way for air to get in and out of the grill. A good charcoal grill can be shutdown when you are finished cooking to put out the fire and save the remaining charcoal for the next cook out. Otherwise you will end up spending a lot more on charcoal than you need to.
When you talk about charcoal grills, the first thing that will jump up is the Weber Kettle Grill. This is the best selling charcoal grill on the market. They usually come in 18, 22 and 26 inch sizes. These grills are very versatile and easy to use. Basically it's a large metal ball on legs. The round shape focuses the heat and reduces heat loss to the outside air. By building your fire on only one side of the grill you can cook indirectly and with a little practice you can even smoke foods on one of these grills. Though gas grills are now out selling charcoal grills, the Weber kettle is still one of the best selling grills on the market and are available practically everywhere.
The Weber Performer combines much of the simplicity of use and convenience of a gas grill with the real fire flavor of a charcoal grill. The Performer is a kettle grill, built into a large stand with a big table top. It also has a 1 pound propane system for igniting your charcoal, so no more lighter fluid. The removable ash can makes clean up also very easy. Now where you can get a kettle grill in the $50-$80 range, the Performer can run around $300-$400 depending on where you live.
Another popular choice is a Kamado grill like the Big Green Egg. These large ceramic units are perfect for not only great grilling but also smoking. With a Kamado style grill you have great heat control so you can decide the temperature you want to be cooking at. Of course you are looking at a lot more money for one of these but it is an investment that is worth the money if you intend to do a lot of cooking.
Because they don't have a lot of moving parts, charcoal grills last longer than gas grills and give you a more authentic flavor. Of course they take longer to get going and lack the convenience of a gas grill. Also, while charcoal grills tend to be less expensive than gas grills the fuel cost is higher will balance out the equation over time.