Yohan Dsouza shows how you can use Maya’s Render Setup to create an AO pass.
Maya’s Render Setup is a much more flexible, well thought out system than the older Render Layers that it replaced. Old habits die hard, though, and some may be more used to the render layer ideology than the render setup one, even after more than a few iterations since its release.
Need to render an AO pass? Then have a look at this new tutorial from DSZ arts (Yohan Dsouza), who walks us through Render Setup to create an Ambient Occlusion pass.