Word Usage
One word, not two
Usage questions ask whether you chose the right word, not whether the sentence is grammatical. Two failures dominate: confusing look-alikes and saying the same thing twice.
Commonly confused pairs. Affect (verb: to influence) versus effect (noun: result); accept (receive) versus except (excluding); advice (noun) versus advise (verb); principal (main; a leader) versus principle (a rule or belief); complement (complete) versus compliment (praise); ensure (make certain) versus insure (buy insurance); lie (recline) versus lay (place something); fewer (countable items) versus less (quantity); then (time) versus than (comparison); imply (the speaker suggests) versus infer (the listener concludes).
Redundancy. Advance planning, end result, past experience, each and every, basic fundamentals, completely eliminate, return back. Each pair says one thing twice; keep the shorter, sharper word. The same instinct applies to inflated diction: utilize becomes use, at this point in time becomes now, in the event that becomes if.
Prepositions and idioms. Comply with, agree with a person, agree to a proposal, different from, consist of, capable of, responsible for. These are fixed; a wrong preposition is a usage error even when the meaning survives.
Worked example: We need to insure that all new employees recieve there badges before they're first day. Three errors - ensure, receive, their - and none is about sentence structure.
Rule of thumb: if you can cross out a word and the meaning is unchanged, cross it out. If two words sound alike, ask what job each one does in the sentence.