The exact rules SAT and ACT writing items test, over and over.
Subject–verb agreement
Singular subjects take singular verbs; plurals take plural verbs. Ignore prepositional phrases between subject and verb — the subject is never inside "of ____".
Pronoun–antecedent agreement
A pronoun must match its noun in number and clarity. If the antecedent is singular, the pronoun is singular; if it could refer to two nouns, the sentence is ambiguous.
Comma rules
Use commas: between items in a list of three or more; after an introductory phrase; around a nonessential clause; and before a FANBOYS conjunction (for, and, nor, but, or, yet, so) that joins two independent clauses.
Semicolon vs. colon
A semicolon joins two complete sentences with no conjunction. A colon introduces a list, definition, or explanation — and what comes before the colon must itself be a complete sentence.
Apostrophes and possessives
Singular possessive: add 's. Plural possessive ending in -s: add only an apostrophe. "Its" = possessive, "it's" = it is. "Their/there/they're" — keep them straight.
Dangling and misplaced modifiers
The word right after an opening modifier must be what that modifier describes. "Running late, the bus was missed" is wrong — the bus wasn't running late.
Parallel structure
Items in a list, comparison, or paired construction must share the same grammatical form: noun/noun/noun, or -ing/-ing/-ing, or to + verb / to + verb.
Verb-tense consistency
Keep tense steady within a sentence and paragraph unless the time frame actually changes. Switching tenses without a reason is a classic trap.
Transition-word logic
Pick the transition that matches the logical relationship: addition (also), contrast (however), cause (therefore), example (for instance). Read the sentences before and after — the meaning, not the sound, picks the answer.
Concision and redundancy
Shorter is almost always right when the meaning is preserved. Cut duplicated ideas ("annual yearly tradition"), filler, and phrases that repeat a word already in the sentence.