Cast iron rusts. Rust is the enemy, it is vitally important that you carefully clean and immediately dry your dutch oven after each use. Now if you have an aluminum oven it's a whole different story but any amount of moisture left on the surface of your iron oven will oxidise. It doesn't take long for rust to form, it can happen right before your very eyes. After I wash and rinse my ovens I take a paper towel and dry every nook and cranny, including under the lid handle, between the raised lettering and where the wire bail attaches to the sides.
Everybody has their own way of cleaning their dutch ovens. Some chuck wagon cooks insist on only using salt, some spray vinegar and water on baked on food while it is still warm, and most everyone will tell you never to use soap in your cast iron. I must confess I do on occasion use dish soap to clean my ovens. When I do, it is usually after I have cooked something that has left a lot of grease behind in the pot. I use a tiny droplet of detergent, swish it quickly with a brush or plastic scrubbing pad, rinse it with hot water and dry. If there's a stubborn baked on crust, I first try my little plastic scraper made especially for dutch ovens. If that doesn't do the trick I heat the tea kettle on the stove, pour in an inch or so of boiling water, scrub it gently with a long handled brush, rinse again with hot water and dry right away. Pouring cold water on hot iron can crack your pot and vise versa so be careful of extremes in temperature.
I lightly oil or spray my ovens before I cook in them, oiling them after cleaning can cause the oil to become rancid. Store them with a folded piece of paper towel inside to absorb the excess moisture and to be on the safe side, I crack the lid to keep the air circulating inside. The best way to care for your ovens is to use them often. Most of the top companies now sell preseasoned ovens, all you have to do is open the box and start cooking. I tend to baby my pots but I have to remind myself that people have been cooking with cast iron for centuries. For generations dutch ovens have been buried in the ground, driven across the plains and scorched in campfires around the world. With a little bit of care your dutch oven will serve you well and give you a lifetime of enjoyment.