Just some common sense in addition to all the regular safty precautions under the car:
(1) Do not overtight the oil pan mounting screws. It is very important. If you bent the pan, you have to buy a now one.
(2) Besure you have a new copper O-ring for the drain plug.
(3) The drain plug usually reqires an allen wrench to open. If the allen head is in bad shape, get a new plug ready before remove the old one.
(4) Do not overfill the tranny.
(5) Do not leave hair fibers in the oil pan when you clean the inside.
(6) Do it when it is hot but burning hot.
I cannot think of anything else now and have fun with it.