Advent should be distinguished from arrival, advent meaning an epoch-making arrival.
Affable means "easy to speak to" and should not be confused with agreeable.
Affect should be distinguished from effect. To affect is to influence; to effect is to cause or bring about.
Aggravate should not be used for annoy or vex or provoke. It means "to make worse."
Ain't is a corruption of am not. It is inelegant though grammatical to say I ain't but absolutely incorrect in other persons and numbers.
Alike should not be accompanied by both as in the phrase "They are both alike in this respect."
All, All right should never be written alright. All and universally should never be used together. All should not be accompanied by of, e. g., "He received all of the votes." Be careful about the use of all in negative statements. Do not say "All present are not printers" when you mean "Not all present are printers." The first statement means there are no printers present, the second means there are some printers present.
Allege is a common error for say, state, and the like. It means "to declare," "to affirm," or "to assert with the idea of positiveness" and is not applicable to ordinary statements not needing emphasis.
Allow means permit, never think or admit.
Allude to is not the same as mention. A person or thing alluded to is not mentioned but indirectly implied.