How can I be a professional photographer?

The only difference between a professional and an amateur photographer is that a professional does it for a living - full time.
Becoming a full time photographer depends on what kind of work you are interested in doing - be it studio work, freelance or working for an agency - it takes time and effort to be recognised and appreciated.
Till then you could try and work on your own style of photography which would make you unique from others.
A good foundation of the studio techniques and old-school lab work would help you understand post processing easily.

Becoming a full time photographer requires a lot of courage and insistence, specially in the Arab world, because photographers are not being paid a good attention, that's why you need to have a strong ambition to become a professional photographer, start a website for your photographs for a start and let people communicate to you, you have to cross you way online at first, so you can get some good offers and a way that would make people appreciate your art, good luck.

there are all kind of professional photographers as nabil mentioned earlier, you have to decide what are you specifically interested in.
Granted, it requires a great deal of money, time and dedication to become a professional photographer in your field of interest, but it sure doesn't help to wander around taking random projects just to become a photographer.
you should find your goal first, and walk towards it one shot at a time.

You should have the soul which record natural art with special taste

you need to have the talent...and then you need to take a course and be committed to your talent.
also you need to LOVE everything around you to see it beautiful..:)

working hardly , read and watch everything about photography , looking for photo of others photographers , try some idea with your self .
LOVE IT .