Well, there's different parts to hacking, most hacks, have a team (unless you know how to do EVERYTHING PERFECTLY) each person has a different job, (Some people have more than one) the jobs I can think of are:
Spriter: Makes pokemon, trainers, etc.
Scripter: Make events happen. (Like being confronted by someone)
Mapper: Make the maps.
Tile Designer: Make tiles for the maps, sometimes the mapper is the Tile designer.
Sprite Inserter: Insert sprites lol.
Beta Tester: Test the game and look for bugs/glitches.
I personally am a Spriter :P