After selecting the “best” image from a shoot (the best portrait from a series for example), I will typically assign a “Pick” flag . Likewise, I might flag any images that I want to delete with the reject flag. Tap the “P” (or the tilde “~”) to add a Pick flag, “X” to apply a Reject flag, and “U” to unflag an image. Use Command + up/down arrow (Mac) | Control (Win) + up/down arrow to increase/decrease the flag status.
When I need several different levels of distinction between images (editing a wedding for example), I’ll assign Star ratings (three stars for hero images and two stars for supporting detail shots for example). Use the numeric keys 1-5 to apply star ratings and the“[“ and “]” to decrease/increase star ratings.
When I’m trying to remind myself that a file needs special attention, I use the numeric keys 6-9 to apply Color labels (sorry, purple doesn’t have a shortcut).
You can create as many different Color Label sets as needed for different photo shoots (Metadata > Color Label Set > Edit). However you should know that as you change sets, images marked with labels from other sets will appear white. To find images with labels from other sets, use the Metadata option in the Filter bar (in the Grid view in the Library module) to quickly search on different labels applied to images from different sets. You can also see what Label is applied to each image in the Metadata panel. One word of caution, if you wish to maintain compatibility with labels in Adobe Bridge use the same names in each application.
Holding the Shift key or turning on the Caps Locks will auto-advance to the next image after applying a color label, flag or rating.