Tilt the cup keeping it on the counter so it stays nice and still. (You do not have to do this in the long run, but it helps at the start). Raise the pitcher up about 6 inches above the cup and pour aiming for the center of the coffee. The goal is for the milk to puncture through the crema and pour under the crema. Gradually lower the cup to the counter so that it does not overflow.
Ideally you will soon see a white bloom in the coffee come up. At this time you lower the pitcher down close to the surface and gently shake it back and forth. There are two common mistakes that beginners make now. The first is they slow the pour down too much as they try to pour the rosetta. You want to keep the flow at a steady rate throughout the pour. The second mistake is trying to steer the milk too dramatically. The motion of the hand is very small. Although the pitcher moves back and forth visibly the hand barely moves. I remember a trick from school when I was little where you had a coin taped to the bottom of a string and you would tell people that it was magic and could tell the difference between boys and girls. If boys held the string it would go in circles and if girls held it would go back and forth in a line. The amazing thing is that it actually worked most of the time. The trick was, of course, a psychology trick. If you think it should go in circles it will and if you think it should go back and forth it will. An amazingly subtle motion is amplified by the time it gets to the coin and the same is true for the pitcher. It might be slightly less subtle, but not much.
Here is a link to a short video that shows a nearly perfect pour of a rosetta. Look how subtle the hand motion is when moving back and forth.http://www.youtube.com/watch?v=j-hu0PXPsMo&feature=related
There are, of course, other forms of art to pursue that are easier such as apples and etching and we will try to include those at a later date, but I thought I would start at the top.