Fastest way to enter a common misspelled word in
AutoCorrect:
When you notice that you just misspelled the last
word...again...all you have to do is press
the left arrow to place your cursor anywhere in the word and
press Shift + F10
to open the right-click menu. Bypass the
suggested word at the top and arrow down to AutoCorrect, then arrow
right and press
Enter on the suggested spelling.

Your
word is automatically added to AutoCorrect. And you
did it without grabbing for that mouse!
Note:
You will see the
AutoCorrect menu item only when Word has a suggested spelling to
offer.