Previously I'd just used multi-sub object materials with simple box/cylinder mapping to texture my models relying on materials rather than textures. I knew this wasn't the way game assets were textured and it was a big gap in my 3D skillset. I shouldn't have been worried about the process, once I learnt the tools in Max they made the process much easier.
To begin with I had to optimise and remodel my character base mesh, some of the armour pieces were separate elements from the main body of the mesh where they would be better extruded from the base mesh itself. This would keep the topology clean for animation, reduce the poly count of the model, and help simplify the UVWs, but keep the overall silhouette of the character.
Once I was happy with the optimising I applied a 'UVW unwrap' modifier, to the mesh in Max. With all the UV's selected I used the flatten tool in the UV editor with a polygon angle of 80 degrees to flatten the mesh onto the UV texture space. As you can see it does a good job flattening the mesh but it's certainly not readable for use by a texture artist.
From there it's a question of selecting each part of the mesh and then stitching them together, it's up to the modeller how the UV's are laid out but it's important to make the final UV map readable, for example the chest-plate is stitched back together to create all one element as it would be in the real world. This is also where texture space comes into play elements can be scaled so they are all the same size using the normalise button but then areas such as the face can be scaled up a little to allow for more detail, although for now my character is wearing a helmet so the I haven't given him a face. It's something I plan on doing especially if the game narrative requires him to take off the helmet at any stage. Once each element is stitched back together they are then relaxed to avoid stretching the texture.
From the UVW editor window you can render and export the UVW map, to an image file. This image file can then be opened and textured in Photoshop, and then reapplied as a material in Max. This means you can work on texturing the file in Photoshop and it's updated in real-time on the 3D mesh. I already knew what I wanted my character to look like from the work I had done on my character sheet, so I created what is known as the first colour pass, it helps to quickly see how your character will read with lighting applied in 3D.
I added additional details such as bolts using the bevel tool in Photoshop and added other details such as edge scratches on the metalwork, and seams and clasps on the leather elements.