How do I know if I would be a good dancer?

Listen to me, no one, but NO ONE that is not a professional can't tell you that you suck. All that takes to be a good dancer is lots of hard work(and of course not be deaf and listen to the rhythm & music). Everybody sees only the result, not the hard work people put into their dreams. So follow your dream and practice, practice, practice. You can even find some dance moves on Youtube.