Watch the Polka Dots and Moonbeams online guitar lesson by Mimi Fox from Jazz Performance
Students are often perplexed by how to develop these complicated lines. The trick is to remember that you start with one good idea, and then gradually add more ideas until you've created a great long line with much shape and interest. If you practice slowly, you can make up your own phrases and use your ear to determine whether they work or not. They have to make sense with the chord that they are being played over.