How strong are you? Dutch ovens are heavy. The Le Creuset 7.25-Quart Round French Oven, for instance, weighs a hefty 13 pounds. The bigger the pot, the more unwieldy it will be, so you'll need to balance capacity against the amount of weight you can easily lift.
How much maintenance are you prepared to do? Dutch ovens with an enameled outer coating are much easier to maintain than plain cast iron. Enameled pots clean up easily with soap and water and can even be put in the dishwasher. Cast iron, by contrast, must be hand-washed with minimal soap -- never scrubbed or soaked -- and then rubbed with a light coat of vegetable oil after each use. Although most cast-iron comes preseasoned (coated with a layer of baked-on vegetable oil), reviewers recommend seasoning them again at home before use, a time-consuming and sometimes messy process.
What do you plan to cook? If you want to cook acidic foods, such as tomatoes, then you'll want a Dutch oven with an enameled finish. Plain cast iron, even after seasoning, may react with acidic foods. If you're going to be using your Dutch oven for baking, then you may prefer a plain cast-iron pot. Many enameled cast-iron Dutch ovens have a composite (plastic) knob on the lid that can become damaged in hotter ovens. If the pot you like comes with a knob that can't handle high oven temperatures, consider unscrewing it and replacing it with a food-safe metal knob.
Do you plan to cook outside the kitchen? For camping use, experts recommend a Dutch oven with a bail (looped wire) handle, which is easier to lift with one hand. Dutch ovens for camping use may also have legs, which allow them to be placed directly into the fire, and indented lids that can hold hot coals. In some cases, the lid may flip over to serve as a griddle.