Crabs and lobsters are things that people rarely cook and prepare at home, and this is something of a pity. Cooking-simply involves boiling in heavily salted water, while preparation is principally a case of getting the meat from the shells. This is time-consuming rather than difficult, and an activity where practice does indeed make perfect.
Start with a crab, which is cheaper. You will be cooking it in its live state. Be brave and look him in the eye, remembering that a watery grave is entirely appropriate for a sea creature. If it is not long from the sea a crab can move with surprising speed so when picking it up do so with conviction, gripping the shell from behind. Drop one and it will shed a claw out of sheer spite.