Step 1: Make sure you are an all-around strong rider with strong legs.
Step 2: Identify drops of about 5' + and work your way up. Don't think that you can drop cliffs like on a snowboard with powder landings. This is mountainboarding - you land on dirt. The largest rideable cliff drop will be about 20' vert and that is for baddass riders. Good candidates for jumpable cliffs are not only sheer drops but they have good and safe run-out areas. A good cliff drop will not only have a decent drop but a good angle to land on. The steeper the angle, the easier the drop. People can drop off anything but the key of course is to ride it out. In addition to a good landing angle the landing must be solid. The more hard-packed the landing is the easier it will be to stick the landing. The softer the landing the more you will sink and usually get thrown forward on your board.
Step 3: Make sure as you head into the drop you are confident. Basically don't chicken out at the last moment and just fall off the cliff. Just say to yourself "I'm gonna stick this sh_t! And do it."
Step 4: Now that you are committed to the drop make sure you have enough speed. Speed is your friend. Stay forward on your board and get ready for the impact. Absorb the impact, regain control and ride it out.
Step 5: Celebrate, bask in the glory, do it again and make sure to get the grab this time.