There really aren't too many ways you can clean a dutch oven. Some people use fire to burn them out. others have been known to try salt. There are even those that just use some dish soap and H2O. If you ask me what the best method is, I would have to say soap and water.
Don't be fooled by people telling you that soap and water will ruin the dutch oven. Even if you have heard this, it isn't true. Well, not completely. Allow me to share with you this: Many years ago I was able to go to a presentation by a very aged cowboy who also used dutch ovens to cook his meal. He was always out herding cattle and would not only use his dutch oven to cook, but to clean the rest of his dishes as well. He told about cattleman who carried a dutch oven on their trip to prepare their tasty food. He said that they had 2 reasons to bring along a dutch oven; for both cooking and cleaning. They would put it on the fire to heat up the water. Right after, they would do their dishes right in the dutch oven and they used soap. Now this is the key. After they finished doing that, they would take the dutch oven and grease it all up so that it would be ready to be used for the next time they needed it.
Now, let's say you don't have any water and still are certain you are going to clean the dutch oven. What do you do? If it was me, I would probably try to burn it out, if not, you can always try to rub salt in it.
Now, if you ever let someone borrow your dutch oven, make sure you tell them how you want it cleaned! I learned the hard way with this one. In fact, my dutch oven was nearly ruined by the people I let borrow it. They tried to burn it out because they weren't sure if I would be okay with them using soap and water. What a horrible consequence! I nearly had to bury my dutch oven and never see it again. Nevertheless, I worked long and hard to get the yucky black charcoaled mess out of it. After a few hours of endless torment I was able to get it back to a fairly good condition. Well, at least it was good enough to cook in again.
Many people prefer salt, including an old friend of mine. it is too bad that he has to spend hours trying to burn out the rust before he can use them another time.
When I am finished cleaning my dutch ovens they are good to look at and store free of rust, ready for whenever they are needed. I enjoy using the old cowboy manner. The dutch oven gets heated while water is in it. After you have completed heating the water into your dutch oven, add a little soap. Scrubbing out the food should be very easy. Rinse it and turn it over to allow for faster drying. When you're dutch oven is dry, take some oil and rub it into the oven and lid. This is vital to the condition of your dutch ovens.
Here is perhaps the most important step.
It is also a good idea to put a sheet of paper towel in between the lid and the oven so that the moisture will be absorbed by it.
This technique has worked wonders for me. The cast iron Dutch ovens stay rust free and ready for use. It doesn't matter what you are cooking your dutch oven over, this method will always work. I've used a charcoal grill, briquettes, and even a camping stove to cook my food with.
So there you have it. Whether you knew it already or not, soap and water is the only right way for cleaning a dutch oven. The only thing you have to worry about when using this method is that the oven is always dry and oiled when it is stored away. That is the biggest secret. If you forget to oil it, well, good luck and don't come asking me to help clean it.