I used to be pretty lazy about renaming Photoshop layers. But then I started kicking myself as I went back to some earlier photos and I couldn't figure out what I had done in several of my post-processing steps. This can really be a problem for those destructive layers (not every tool can be applied non-destructively) if you decide to make changes and have to recreate certain layers.
The way I get around this is to record as much information about that layer right in the layer name. For example, when I sharpen a photo (typically at the final step), I'll basically create a new layer that contains all the combined information from the layers below (Stamp Visible). Then I'll apply the Unsharp Mask to that layer so I can retain all the previous work within the Photoshop file. After applying the edit to that layer, I rename it to include all the parameters I need in case I want to recreate it or modify it. So it might look something like “Unsharp – 87 – 3.3 – 1”, which means Unsharp Mask at 87%, 3.3 pixels, and a threshold of 1.
Non-destructive layers and adjustment layers are a bit easier to figure out with just the default layer names, but if you have 4 or 5 of the same adjustments on top of each other it might get a little confusing. I'll run into this type of thing when I do a lot of dodging and burning with curves adjustment layers and masks — so I rename each layer to tell me which area of the photo it applies to (sky, ground, wall, house, clouds, etc).
It's not necessary to rename every single Photoshop layer, but it's not a bad habit to rename the less obvious ones.