While every designer has their own method for Photoshop renderings (and I'm by no means an expert), I do get a lot of requests for the process that I typically take to create a presentation rendering. I've put together a little tutorial to show the steps I use.
Click the Read More link below for all 6 parts of this tutorial.
**one note- im doimg this tutotrial from a finished rendering "in reverse" so if you look at the layers or path palettes you will ALL the final layers/palettes that exist at the end of rendering. ive just "un-viewed" the layers to work backwards to show how its done forwards. just so nobody gets confused. (R)
To start with, I make do a sketch of the shoe I am going to render to use as an underlay. The more in proportion and accurate this sketch is, the easier it is to do the required line art which will be used as a template for the rendering.
Using illustrator, I place the scanned sketch in a layer and dim the image (under layer > properties). Then using the pen tool, I draw over the image, making frequent use of the pathfinder (cut, intersect shape areas, add to shape areas) tools.
This line art can then be cut and pasted into photoshop. I cut and paste the same artwork twice. Once as a Path, and once as pixels. The paths are used as cutting paths and masks for the rendering, and the pixels just give a good quick easy overlay/underlay to the rendering so you can see whats going on.
From the path palette, you can select (using the black arrow path modifier tool) different parts of your work path (I usually rename to "All", or something like that). Once you have part of the body shape you want (I start with an outline shape that is whole upper), you can cut and paste that path to create a new path (renamed Body).
This path can then be selected (the little button at the bottom of the Path palette with the dashed line circle), and you can make a new layer to start painting into. As I work, I find it important to keep my layers and paths well organized and named (instead of "Layer 38"), so its easy to find them later. By the end of the rendering I typically end up with something like 30 paths and 60 layers, so having some meaningful name helps a lot.
Once you have a new layer, and a selected area, you can use the paint bucket tool to paint a solid color base for your rendering.