Use Keyboard Shortcuts

Everything on your Mac seems to be mouse-centric. But the Mac also features hundreds of useful keyboard shortcuts for accessing the menu bar and other clickables. In addition, many Emacs-compatible and almost unknown keyboard shortcuts work in every Cocoa application, e.g. Control-T for exchanging the character in front of the cursor with the one after the cursor or Control-K for deleting until the end of the line.

See Apple’s knowledge base page listing all system-wide keyboard shortcuts.