Creating a map for your 3d model can be a complicated or simple process depending on what you have modeled. The process is similar; however, and only becomes complicated with adjusting the map so that it is easier to map in Photoshop or any alternative. The first step to creating a skin or map for your 3D model is to render one from 3Ds Max. Click your model, apply the UVW unwrap modifier, click UV edit, and project the model correctly . You may need to add an Edit Poly modifier for every side of the model to be projected correctly. These modifiers can then be collapsed and opened up again with another Unwrap UVW modifier. Arrange these UVs in a way that makes since to you when you apply a texture to it. Click Tools, and Render UVW map after you have projected the map correctly. You should render this as a jpg or png and on another layer, use the UVW Map as a guide for how to map the 3D model.
The Next step is applying your made map to the model. To do this click the Material Editor or press the M key on the keyboard. Using this view you can apply your maps on the model's sides.
Here is an example of a well mapped model. The hardest part of mapping the robot was figuring out how to collapse the UVW correctly so I can organize the maps correctly. After rendering the maps, editing them in Photoshop, and reapplying them to the bot, I was able to adjust the maps from the UV editor as needed and finish a good product.
Summary
Mapping is a simple but tedious process
UVWs guides are technically made for you to play around with and texture