The trees vary slightly from team to team, but generally speaking, even numbered routes break inside and odd numbered routes break toward the sideline.
Here's a look at the West Coast route tree:
This image shows typical routes for both the X and Z receivers. The numbered routes also have commons names:
0: Hook
1: Flat
2: Slant
3: Out
4: Curl
5: Hitch
6: Dig or In
7: Flag
8: Post
9: Go
The Air Coryell route tree looks similar, if a little more basic:
Here, you see the similarities (and the differences) between the Coryell and the West Coast systems. With more intermediate and horizontal routes, the West Coast offense tries to stretch the field horizontally more-so than vertically, like the Coryell system does.
Outside Resources:
1) West Coast Offense
2) The Spread Multiple West Coast Offense
3) Saints Football 101: Receivers, Routes, and Personnel
