-Use spell check. Word processing programs have this amazing button that actually goes through your document and checks for spelling errors! USE IT!
-Sometimes spell check misses things, but that is because the word is spelled correctly. However, it's not the word you want to use. Read over your document a few times to check for words that are spelled right, but are the wrong words to use.
-Make sure you use commas and apostrophes in the correct place. Use the AP Stylebook for these guidelines.
-Use the correct form of a word: they're / their / there, to / too / two, then / than, your / you're, etc.
They're going to the beach. This is their house. There is a cat.
I'm going to the movies. We are coming with you, too. I have two umbrellas.
They went to the movies, then they went out for ice cream. My dog is better than your dog.
Is this your car? You're going to love this restaurant!
-Keep reading over the document. Have someone else look over it for some fresh eyes too!