I started by breakingdown the layers into what I already knew was needed. Diffuse, Reflections, Shadow, AO, Zdepth. I then thought that by splitting up the tents from the ground I could get more control when it comes to compositing. It meant that I could correct both the colour and the shadows of the tents seperately to the ground. I also had to split up the trees from the render as they will also need to be tweaked in After Effects. I got rid of the specular pass because I didnt think it was necessary until it came to rendering the characters. I also got rid of the Zdepth because I was having troubles getting that but I will go on to that later. Finally I knew the ObjectID pass would be needed for selecting and masking in post-production. Here is a screenshot of my render layers so far.
Splitting up the diffuse pass (or beauty pass I should probably be calling it) and the shadow pass was slightly frustrating at first because I hadn't got to grips with the render layers yet. To do it I basically selected everything in the scene except for the mountains, props and trees and created a new layer and called that ground_diffuse. I duplicated this and renamed it Ground_shadows. To remove the shadows being casted onto the objects in the diffuse pass I selected all the objects, headed over to the attribute spreadsheet, then render, then selected recieve/cast shows and set that to Off.
In the Shadows pass then I had to select all of the objects and assign a UseBackground shader to everything. I reduced the reflectivity to 0 and the reflection limit to 0.
Of course ... for most people this is probably a simple thing to do. For me ... Maya had other plans. I managed to hit a pretty big set back here. I came across this problem where Maya would simply remove all shading information on some of the props in the scene when ever it liked. It seemed as if it was only doing it when I applied the UseBackground shader to the props. This is very stressful when you have spread out hundreds of leaves with 5 different textures on them and it deletes there shading networks. I was forced to applying different textures to each individual leaf ... only for Maya to remove them once again. Anyway to cut a long story short I ended up deleting the history on the props which despite removing the shading again it seemed to have removed the weird bug I had going on.
If there is one thing you should learn from this .... it's to regularly DELETE HISTORY!!!