Choose a tag. This is the graffiti name that you will be known by. Short tags are more common, as are numbers, for example: BEAT 23.
Select a style of graffiti letters. Do you want fat letters that look like balloons, or skinny, angular letters that have hooks and barbs?
Do a sketch of your tag with pencil and paper. Use this sketch to plan out how your characters will touch or intertwine.
Determine where the shadows of the letters will fall and fill them in.
Clean up your paper, erasing any hesitation marks you might have made.
Outline your finished tag in ink, and create a border around the entire tag. The border can be anything you want--crackles of electricity or radiating lines of color are popular choices.
Fill in the tag with color. Use paint or markers.