I've had a couple people ask me how to do Ambient Occlusion in maya and so I've desided to make a tutorial on it!... Though I'm not sure if this can work in any version of maya lower than 7.. Here is a good explanation of what it is http://www-viz.tamu.edu/students/bmoyer/617/ambocc/
Start up maya. Import the model you want to render with AO (ambient occlusion) if you want you can create a little stand for him to stand on like did. But if you're not going to import your model, create two spheres close to each other, almost touching also you can create a plane for the ground if you'd like
Now go to your hypershade editor by clicking this button your tool bar
Once you've got it up, make sure you're in mental ray nodes (Create Mental Ray Nodes should appear on the side, if you see create Maya Nodes, click the little black arrow and click Create Mental Ray Nodes up at the top of the hypershade editor) Click materials, and click mib_illum_lambert (if your attribute editor is not open on the side hit CTRL+A to get it up) and change it's settings to look like this:
Now go back to your hypershade editor and scroll down to Textures, click mib_amb_occlusion you should see it in the lower half of your hypershade editor as a white cube, in your attribute editor you should now see your ambient occlusion settings apply these settings to it:
Click on the cube with your middle mouse button (if you don't have a scroll where I don't know what other button works >_<) and drag it on top of your mib_illum_lambert you should then see a little menu pop out with a few selections, choose ambient. Now what I did was I changed the background color of my perspective camera to a light gray for those of you who have darker monitors it would be easier to see (I would hope) so to do that go to the menu on your perspective view port and click view>Camera Attribute Editor... and the cameras settings should pop up in the atribute editor, scroll down to environment and make it a light gray.
Now that we have our lambert and ambient occlusion shaders attached, we should assign them to our model! Select your model and/or plane/stand if you made one, make sure you're in the rendering toolset, and go to lighting/shading>assign existing material>mib_illum_lambert. Ok Now what we need to do is go the render globals 
and select mental ray from the "render using:" menu at the top. Go to the mental ray tab and change quallity presets to production, and click render 