Each, Every
“I see him at his office each day of the week.” In this sentence the word every would be better. Each refers to single days particularized. Here reference is made to what occurs on all days without exception.
Both words refer to nouns in the singular, hence such expressions as the following are incorrect: “Every soldier and sailor stood at their post.” “The prisoners were discharged and went each their several ways.” Correct by saying, “The prisoners were discharged and went each his several way,” “Every soldier and sailor stood at his post.”
Each, Both
“Both parties maintained their original positions.” As the parties are thought of separately, the sentence should be: “Each party maintained its original position.” “Both parties strove to place their best candidates upon the ticket” is correct, because the parties are thought of collectively.
Both, Both of
Both is used alone before nouns and both of before pronouns. “Both men have studied the currency question.” “Both of them are well informed in matters relating to the currency.”
Ever, Never
“Let him be ever so rich,” says Emerson. “You spend ever so much money in entertaining your equals and betters,” says Thackeray. “Though he run ever so fast, he cannot win the race.” Writers and grammarians differ, some preferring ever, others never.