[LWC]

To me, and what I have seen, takes a combination of a few things:
1. The Look
A wrestler has to have a certain look. If they are the scary Taker/Kane/Khali figure, they need to look it. If they are the pretty-boy, the muscle-man, the diva, etc... gotta have a certain look.
2. Charisma.
Self-Explanatory
3. Character Vision
All the time stories are told of wrestlers that have an idea for a character, take it to McMahon or one of the writers and it happens. Stone Cold is a great example.
4. Legacy
Many guys like Orton and Rock may have never had a shot, if it wasn't for legacy. It is not essential, but it sure helps.

There are goofy characters that end up changing and making it big (John Cena is a great example) so a guy like Zack Ryder can make it.

Takes a lot of luck, a lot of skill and a lot of hard work to make it.