An interesting question.
I've been doing studio photography (and earning my living from it) for so long now that I can't remember the details. However, I was a studio trainee when I started, so I didn't have to pick things up as I went along and rely on (often totally wrong) forum posts for info.
What I find interesting is that I started out using continuous lighting, because there was no choice. When electronic flash became available it was horrendously expensive, pretty poor and extremely bulky but we all jumped to it because it was so much better - and yet there are a lot of beginners now who seem to think it's better...
3 things strike me as common problems for beginners
1. They don't understand that the shutter speed is almost irrelevant as long as the shutter is open at the time the flash goes off. It's impossible to get worthwhile results unless there's a basic understanding of the technicalities, and it doesn't get much more basic than that.
2. People don't seem to understand that they live on a planet with only 1 sun. They understand that with outdoor photography but immediately forget it when they move indoors, and for some reason feel that they need to use 2 or more lights (2 or more conflicting suns) and don't realise that the results inevitably look unreal.
3. People don't realise that they can only really learn about lighting if they practice on still life subjects. Humans move around, and good lighting is precise lighting, precise lighting is spoiled when people move slightly out of position. Learn HOW to light on subjects that keep still! Also, the success or otherwise of a 'person' shot is usually judged on whether or not that person is attractive and on their expression - this can be frustrating, another reason to practice on still life subjects.
Oh, and my other pet hate is people calling white backgrounds 'high key'
