I'm an especially big fan of grouped layers and adjustment layers. If I want a bunch of adjustment layers to affect only one layer, I just group them onto that layer. For instance, I might have a person on a layer above a background layer, and if I want to tweak the colors and contrast on just the person and not the background, I do it on an adjustment layer that's grouped to the layer with the person. And since that adjustment layer makes any tweak I make NOT permanent, I can always readjust and re-tweak it a bit later, after getting client feedback, without feeling like I lost the critical information of the original. Makes my life sooooo easy. :)