Below are brief examples of what I do when I proofread, pulled straight from work I’ve done. Names have been changed to protect the erroneous.
misspelling: Schaefer & Schaefer is a full-service pubic relations firm. (Yes, that was an actual error I caught.)
correct: Schaefer & Schaefer is a full-service public relations firm.
wrong word choice: The affects of the tornado were devastating.
correct: The effects of the tornado were devastating.
missing comma: It’s snowing people!
correct: It’s snowing, people!
extra comma: The United States fought for the Allies, and led them to victory.
correct: The United States fought for the Allies and led them to victory.
missing hyphen: At that point, Jerkins & Associates will make a follow up call to the client.
correct: At that point, Jerkins & Associates will make a follow-up call to the client.
extra hyphen: “I didn’t sign-up for this,” said Harold.
correct: “I didn’t sign up for this,” said Harold.
The Grammar Geek
copyediting, proofreading