Audience is not the same as spectators. An audience listens; spectators merely see. A concert has an audience; a moving picture show has spectators.
Aught means "anything" and should not be confused with naught or the symbol 0 which means "nothing."
Avenge means to redress wrongs done to others; revenge wrong done to ourselves. Avenge usually implies just retribution. Revenge may be used of malicious retaliation.
Avocation should not be confused with vocation. A man's vocation is his principal occupation. His avocation is his secondary occupation.
Aware is not the same as conscious. We are aware of things outside of ourselves; we are conscious of sensations or things within ourselves.
Awful and awfully are two very much abused words. They mean "awe inspiring" and should never be used in any other sense.
Badly should not be used for very much. It should not be confused with the adjective bad. "He looks badly" means he makes a bad use of his eyes, say "He looks bad."
Bank on is slang. Say rely on or trust in.
Beg is often incorrectly used in the sense of beg leave, not "I beg to say" but "I beg leave to say."
Beside, meaning "by the side of" should not be confused with besides meaning "in addition to."