There are relatively few things that you can do to speed up your editing workflow that are as easy and as powerful as learning the app's keyboard shortcuts. Burn them into muscle memory and you'll wonder how you ever worked without them.
Commercial photographer Brian Rodgers Jr. has compiled some of the most important keyboard shortcuts in this 13 minute video. Besides the general keyboard commands for undo, cropping, etc., Rodgers also dives into the various brush tool shortcuts alongside retouching and selection tool shortcuts.
You can find Adobe's official, comprehensive list of Photoshop keyboard shortcuts here.