Subject-Verb Agreement

Singular subjects take singular verbs. Plural subjects take plural verbs.

Tense Consistency

Keep the same tense within a paragraph unless indicating a time shift.

Comma Usage

Use commas to separate independent clauses joined by conjunctions (and, but, or).

Apostrophes

Use for contractions (it's) or possession (John's). NOT for plurals.

Who vs Whom

Who = subject. Whom = object. "Who called?" vs "To whom did you call?"