You might learn to duck... because I SHOOT that scum that writes graffiti on my street side walls. Grow up and get a real life and don't destroy the property of others because you are bored or too stupid to do anything creative.

well first you have to love what you do and have to love graffiti.
You have to learn how to do it.Try to learn to do pieces and not the lame tags you see around which create an eye sore.
Graffiti is a lifestyle similar to someone loving hip hop all their life or art all their life etc.I have done it for over 20 years now.I done a nice burner piece only 2 days ago in Bangkok facing the trains.It was a legal wall and i pay the owner to do it so you can get maybe 5-10,000 people seeing it everyday.It was nice 3d style.You have to learn to piece first.Get a sketchbook and practise.Do outlines and characters.When i was younger i was lame at characters but still practised on paper anyway for years and years .Now my character's are dope.You just gotta stick with it and don't give up!
Good books would be Subway Art by Henry Chalfant or Spraycan Art by Henry Chalfant.These are the original oldskool books of where it all came from.Good web sites would be:12 oz prophet.com or Aerosoltalent.com also do a graffiti search for Daim or Peeta.Daim is recognised as possibly the best writer in the world and Peeta's work will blow you away too.Any more advice let me know.Good luck.P.s if you want ,one of my pieces was chosen the best out of about 2000 on one of the editions of aerosol talent i will find out what edition so you can see!