Since the integration of mental ray in Maya may obscure modern workflows, many of the posts here explain how to make the correct choices. But typically we assume some prior knowledge of Maya and mental ray.
We will begin a series soon on how to make modern choices and avoid pitfalls in the UI (like the default absence of shadows, no passes with materials unless using the *_passes materials, etc).
If you have experience where you have had difficulty tracking down a problem only to discover it was a checkbox or some other snafu, leave that here in the comments with a short description. We can use this information to make new users more efficient and help refresh the rest of us too. We will try and include this in sections explaining basic scene setup. Our cheat sheet for quickly rendering.
If you are a developer, it might be helpful for you to see where some defaults could be changed and alter the corresponding .mel in your installation to make a new default.
Please keep the comment factual and tidy. We reserve the right to edit it to the essence of the problem. 😉
My passes kept rendering black using the mia_material_x. I discovered I should upgrade them to the mia_material_x_passes shader.