Fabric: fat quarters of light and dark fabrics. Include lots of lights, lots of darks, some yellow, red and some "Uglies" in your selections. This is a great place to use up fabrics you are tried of or want to clear up from your stash. The more you bring, the better; trading will be encouraged. Bring at least 9-12 light and 9-12 dark fat quarters, cut as described below. This is a good starting point.
If you want to precut: cut 3 1/2" squares and 3 7/8" squares from all fabrics.
(If you have boxes and boxes of 2" watercolor squares, bring them. I'll show you how to use them instead of the larger squares.)