Subjects and verbs must agree in number.

Example: The team is winning. The players are excited.

Pronouns must agree with their antecedents.

Example: Every student must bring his or her book.

Use commas to separate items in a list and after introductory phrases.

Example: After dinner, we watched a movie.

Place modifiers near the word they modify.

Incorrect: Walking home, the rain soaked her.

Correct: Walking home, she was soaked by the rain.

Use the same grammatical form in lists.

Example: She likes swimming, biking, and running.

Keep verb tenses consistent.

Incorrect: He starts the car and drove away.

Correct: He started the car and drove away.

Use apostrophes for possession and contractions.

Example: That's Sarah's book. It's a nice day.

Do not use two negatives in one sentence.

Incorrect: I don't need no help.

Correct: I don't need any help.

Use semicolons to link related independent clauses; colons to introduce lists.

Example: She has three hobbies: painting, dancing, and reading.

Ensure comparisons are logical and complete.

Incorrect: She is smarter than anyone in her class.

Correct: She is smarter than anyone else in her class.