Apple iWork '08 - Manual (Page 119)

Chapter 3 Getting Started with Keynote 119
After you choose an effect for each item you want to animate, you can easily change
the order in which the items build. You can also choose whether to begin each build
automatically (after a specified time) or when you click the mouse.
Here are ways to change the order of object builds:
m In the Build Inspector, choose an option from the Order pop-up menu.
m Select “Set separate timings for elements,” click More Options, and then drag items in
the Build Order drawer.
Drag items to put builds
in a different order.
Choose how to start the
selected build.
Specify how long to wait
after the previous build
finishes to start the build.