The first requisite of style is choice of words, and this comes under
the head of Diction, the property of style which has reference to the
words and phrases used in speaking and writing. The secret of literary
skill from any standpoint consist... Read more of DICTION at Speaking Writing.com
Each other refers to two, one another to more than two. "Jones and
Smith quarreled; they struck each other" is correct. "Jones, Smith and
Brown quarreled; they struck one another" is also correct. Don't say,
"The two boys teach one another" nor "The three girls love each other."