Put it away for a while (weeks, months, years…) and look at it again later with “fresh eyes”

Print your manuscript and edit it on paper. You missed something.

Read it aloud. You’ll simplify, you’ll hear things you missed, you’ll confuse your pets and neighbors. All good.

Use the spelling and grammar checkers in your word processor. Know when to disagree with them.

You can use the Search features in your word processor to find mistakes you know you commonly make.

Print it again. You missed something. Moan about the price of ink and toner cartridges.

BONUS TIP:

Four eyes are always better than two. Get a second opinion.