Shading the Objects / Creating Image Based LIghting for the Scene
Section A - The hat 
The way I picture this hat is the following: green velvet with a gold buckle and a shiny black belt. The buckle and belt are easy enough, but do we really need to spend a full day trying to come up with a decent looking velvet shader? Absolutely not. There are a bunch already made that we can find elsewhere. Is this the easy way out? Maybe. But this is a 'Station ID' tutorial. The world of broadcast design simply does not lend itself to spending hours on one shader. A quick search on Highend3d.com finds us a great looking velvet shader here.
If we view it in the Hypershade winder, we can quickly modify the two 'Velvet Colour' Ramps to a festive green and get a pretty decent plush shader.
Now for the other two shaders for the hat: the buckle and the belt. These are going to be Mental Ray shaders.
At this point, we need to switch to Mental Ray rendering. Go to the Render Globals set it to render using Mental Ray.
If you don't see Mental Ray as an option, go to your Windows>Setting/Preferences>Plug-In Manger and make sure that "mayatomr" is loaded.
Pull up the Hypershade window and switch it to "Create Mental Ray Nodes".
We need to create a 'dgs_material'. We'll set the colors on this to be in the yellow/gold side of things. The reflections and such will come later when we add the image based lighting.
For the belt, we'll create one more dgs_material and set the Diffuse and Glossy colors to a very dark gray.
Create an ambient light, setting the intensity to 0, but turning on shadows.
OK... so let's see some results. Go to your Render Globals, go to the Mental Ray tab and find the "Image Based Lighting" section. Click the 'create' button.
You'll see a wireframe sphere appear in your scene. Set the mapping to "Angular". In the Render Stats, set the Primary Visibility to off.
And now we need an HDR image to use. You can find some decent articles explaining image based lighting and sample HDR images here.
Let's try one of these. I am using 'campus_probe.hdr'. So, if we go to the Image Name field of the Image Based Lighting Attributes to select an HDR image.
One more thing before we try a test render, let's adjust our render settings. Go to the Render Globals, let's start with the "Production" preset. Go to the Final Gather section, check the 'Final Gather' box and set the Final Gather Rays to 500.
Apply the velvet, buckle and belt materials to the appropriate objects. Render a frame.
Yippee, the hat is shaded.