How do I design a dry river bed?

All the magazines are thin on giving good advice! I have a blank piece of paper, and a 40 by 40 hill in California. I want to put a dry river bed in it and don't know the first thing to do. I could put a rock here and rock there, but how do I make it look great?
Thanks for your help!

Hi,

Spread a three-inch layer of river rock down the length of the channel, which gives a firm base for the first set of stones. Position the smaller stones along the edge of the channel, working from the bottom up, one or two layers at a time. This process takes a little time, but don't be afraid to move the stones around until you get the look you want.

Good luck.