Complex illustrations tend to produce complex and messy PSD files. Properly managing your layers in Photoshop can lead to better efficiency and a more editable file.
The problem with PSD files is that they can quickly get out of hand. Being careless about naming files or not properly grouping them may save a little time in the beginning. However, once you are several hours into Photoshop, the time wasted trying to find the right layers or make changes far exceeds the time saved at the beginning.
This illustration presents an example of grouping layers. Obviously, the specific groups change from illustration to illustration depending on the type of image.
Groups, Masks, and Adjustment Layers
Groups are folders in the layers palette that contain one or more layers. This is key to a clean Photoshop file. Groups allow you to collapse many layers down to a single line allowing you to navigate between several hundred layers quickly. Another advantage is that you can apply masks to groups which is very useful for editing.
A group can be created by clicking the folder icon at the bottom of the layers palette. You can drag the Layers into the folder one at a time or several at a time.
Masks are essential for nondestructive editing. The idea is to edit the illustration in a way where changes can be reversed later on.
Masking is great when it comes to cutting out backgrounds or removing parts of the layers. Masks are exactly as they sound allowing you to mask or hide parts of the layer similar to erasing. The difference being the mask can be removed later to bring back the area of the layer that was erased.
Adjustment layers act like real layers allowing one to adjust the strength through opacity or even apply a mask to the adjustment. Similar to masks, adjustment layers are nondestructive and allow you to adjust things like levels, contrast, hue, etc. to several layers at once and also reverse the adjustment at any time later on.
Above is a screenshot of the layers palette for this illustration. You will quickly notice that everything is grouped. Having everything grouped allows me to collapse all layers and move around the palette more easily.