I'd say be good with most of the material if your doing commercial(this is tough though because if you've never done xp or something it really isn't your fault), be able to rough in rooms easily, have some pipe bending knowledge, understanding switching and simple wiring, and just being a hard worker is most important.
It really depends what you've been exposed too, if you'e done nothing but office buildings it's not really our fault if you don't know pipework or explosion proof stuff yet. There is a lot to learn. Hopefully you get with a small/medium contractor that does a wide range of jobs. Just be honest when you get on a job and they ask what you've learned, if you bs and act like a know it all no one is gonna help you out.
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