But most of all - shoot. Shoot more and more. Doesn't matter that much what it is, but imo, preferably people. Dealing with people is the hardest part of professional photography, but it is most certainly learnable, but there is only one way of doing it. Go out and shoot. Find every possible opportunity to shoot. Don't worry too too much about financials etc - don't get ripped off, but don't spend your whole life wondering where the next portrait assignment will come from - find a local magazine or something run at low/no profit that wants environmental portraits of people they interview shooting, or events, or or or or or etc.
Build a brand now. Website, business cards. It'll mean that when someone mentions something, you can offer a solution. Don't get vistaprint.
3 years ago I was a shy, nerdy 18 year old with naff all social skills, and went and bought a D40 and a couple lenses with some of my first few paychecks from my gap year job. Last night at a corporate event I made in 3 hours what I used to make in a week and a half full time. Nowhere near 'it', or where I want to be, yet though.
In ten years' time, I will answer your question much better