Learning to draw great graffiti art requires lots of skill and practice. There are several genres of graffiti art, but usually, graffiti art will mostly: -- be painted in vivid colors, to create emotive images and grab attention -- include graffiti style lettering with letters that overlap and are drawn in 3D In particular the use of the bold style lettering is really distinctive to graffiti art. The images themselves will usually be hard hitting, and be painted in stark colors utilizing strong shadows and outlines to add depth and definition. Images usually depict social or political issues close to the artist's heart.
Before you start a piece of graffiti art, you should draw a small scale version of the large piece you want to create first, then when you begin your actual piece, its a simple task of just scaling up your graffiti sketch. If you need ideas for a graffiti font to use, there are plenty of sites online that have examples for you to copy. For the outlines, use a fine marker pen. In order to produce a 3D effect, shade around the letters you've outlined with a different color. Then use permanent markers to color in your letters.