Finally gave in and bought it

What are important need to know things for a new account? what to focus on? what is the best course of action? best classes and specs/weapons? (i never care about the meta, just what is fun for me but it is nice to know) what mistakes to avoid? anything a newbie (but gaming veteran) should know? (every game got its on perks and quirks) thanks in advance!!

EDIT: Thank you all so much for the replies, exactly what i was looking for! Cadet training commences now!