This is a cool way to learn how to draw graffiti in legal areas.
Familiarize yourself with different styles of graffiti. No matter where you live, you can probably find graffiti nearby. If you can't find any in your neighborhood, visit a city if possible and look there--graffiti is predominately an urban art form. If a trip isn't possible, look on the internet. There are hundreds of websites that have pictures of graffiti; you can take a virtual tour of styles from across the country and around the world. Some pieces are obviously better than others, but the more you see the better you'll know the characteristic styles of graffiti.
Write down a name on a sheet of paper. You can start with any word, but your name is probably the best choice. Almost all serious graffiti artists start by developing a unique way of writing their names. As a beginner, it is probably easiest to print the letters and write in all capital letters. Use a pencil, and draw lightly so it is easy to erase anything you don't like. Leave plenty of space between the letters; you'll expand the letters to fill in the space later. Make them big enough to work with, but not so big that it will take forever to complete the graffiti.
Choose a style you'd like to use for the name. Bubble letters are especially popular in graffiti (see the related wikiHow for instructions), but there are plenty of other styles, too. You can have rounded edges or sharp, equally sized letters or some big letters and some small, etc. It's easier to emulate a style, and it's a good idea to have a picture of a graffiti piece in that style to refer to. Once you learn the basics you can develop your own style naturally.
Outline the letters you have written to approximate the style you're going for. Again, use pencil and write lightly. You'll likely make plenty of little mistakes, but that's what erasers are for. It will take time and patience to get the letters just right. Remember:
Make the original words you wrote your guide,
not your prison.
Don't be afraid to alter the letters
beyond all recognition.
Vary line thickness. You can make all the lines the same thickness, but you can approximate shading and a 3-D effect if the lines get thicker and narrower at different places (for example, the top and one side of an "o" might be very thick, while the bottom and other side is narrowed). Use your pencil to vary the thickness; you're going to darken this out with ink or marker later, so it doesn't need to be pitch black. By doing this step now, you can get a good idea of what thicknesses look good before you make the lines permanent.
Add details as desired. Once you have your letters just as you want them, you can add additional details--again with light pencil--if you choose to. Perhaps a lightning bolt for the dot of an "i" would be good, or eyes peering out of the holes in your "b". You can put a bubble around the whole name, like they sometimes do in comic books. The possibilities are limited only by your imagination.
Copy your drawing. We're putting the pencils away now, so everything from here on out is permanent. That means if you make a disastrous mistake--or two, or three--as soon as you put the marker down on your paper, you won't be able to do much about it. By copying your drawing you'll have a backup if something goes wrong. The easiest way to do this is to use a photocopier and adjust the darkness setting so that the light pencil lines will show up on the copy. You can also try to trace the drawing onto another piece of paper, but this will be difficult because of the lightness of your drawing. If you do want to trace what you have, wait until after the next step or trace a photocopy.
Blacken your pencil lines. You can use pen or marker to darken the lines you drew with your pencil. These lines are more or less permanent, so you'll want to be extremely careful. Don't be discouraged if you make a small mistake; you can usually patch these up so that nobody will notice but you.
Add color to fill in your drawing. You can use colored pencil, marker or crayon. Again, it's a good idea to look at examples before doing this, but really you can do anything you want. A very simple graffito (the term for a single work of graffiti) can have only one color. You can also easily do each letter in a different color or make the added details a different color than the letters. While you might be tempted to go crazy with color, sometimes simplicity is best. Graffiti artists traditionally had to work secretly for fear of getting caught--many still do--and so they could carry only one or two different colors of spray paint at a time--a lot of very good graffiti is just one color.
Keep practicing. If your graffito turned out perfectly, congratulations. Now you can move on to different words and effects. If not, keep trying. Master the simple moves first and then work your way up--you'll soon develop your own style.