Before you pick up a can of paint, get a notebook or sketchpad. This is called a "black book", and all graffiti artists have one. Go online or outside and find a piece of graffiti you like. Now copy it down on paper. This is called "biting", and is generally frowned upon, but it's a good way to start. Once you get used to that, try an original design. Then you can get some paint. Start out with cheap paint from a hardware store, and get good paint when you get better. Don't get Krylon, though. It's too watery and the fan-tip is awful. First, practice writing your name on a piece of plywood. Figure out how to do flairs (paint a line and slowly move the can away as you paint the line) and other designs. Then start painting in block letters. Often graffiti pieces have arrows or halos, so you might want to work that in somewhere, but you might not want to. Do your own thing. If you can, get some spray paint caps. These are designed to change the spray diameter. You take the cap off the paint, and replace it with a new one. You can buy these online. I recommend Art Primo. Keep practicing, and tada! You're a graffiti artist. Use your powers for good not evil. Paint on plywood, fabric, canvases, and walls that you have permission to paint on. Don't paint on someone else's property. Not only can it land you in a world of trouble, it gives graffiti a bad rep. I hope this helps. Have fun!