Updated June 8th, 2019.
Most Mac programs mark misspelled words with a dotted red underline, like this:
If you hold the Control key down and click on a dotted-red-underline word, you’ll get a contextual menu, like so:
You’ll see possible corrections at the top of the menu. Choose the one you want and you’re done. This is a million times easier than running the spelling checker.
Bonus: if the word you’ve misspelled is plural, the choices are plural too. Look:
Control-clicking on that misspelled word produces this menu:
This works in Word, Pages, Mail, and just about everywhere else. Try it!