1 Your correctly exposed film. (This always helps)
2 Developing Tank
3 Chemicals: Developer, Stop Bath (You can get by without this) and Fixer. Prepare all of your chemical solutions in advance and according to the instructions supplied with them. Ensure that you prepare sufficient volumes to completely cover the film in the tank. The required volume can often be found stamped on the tank somewhere, usually on the base. In place of a Stop bath you can use a water bath although it is not as efficient.
4 Measuring cylinders or jugs and a stirrer to prepare solutions. You should have at least two measures. Use one measure exclusively for preparing your developer if possible. Cross contamination of chemicals is bad news, particularly getting Stop or Fix in your developer.
5 Storage bottles for solutions. Stop and Fix can be re-used as can some developers.
6 A good thermometer.
7 A film leader retriever or bottle opener to get at your film.
8 A timer. A watch will do but a proper timer is easier to keep track of.
9 Water to wash the processed film. Running water at or about the same temperature as your processing chemicals is best. If running water is not available ( if you are in a shed or something! ) have a bucket of water at the right temperature handy.
10 Wetting agent. Useful but not essential .
11 Two film clips or clothes pegs to hang your film.
12 A bit of patience.