Paths to Shapes

If you paste some illustrator paths into an After Effects Shape layer and the paths are pasted as masks, you need to look at Trish Meyer's essential trick to paste multiple paths to After Effects Shape Layers at once: Pasting Paths from Illustrator to After Effects.

For background, see Shape Layers in After Effects CS3 by Total Training host Steve Holmes at Layers magazine

Update: Motionworks has a 2007 tutorial movie also, Mask to Shape Layer, and Aharon Rabinowitz added a podacst An Introduction to Shape Layers.