The proper salutation for a lawyer is to use Mr. or Ms. followed by the person's last name. The title of Esquire, used in the legal profession, does not need to be used socially.
Esquire, generally abbreviated as Esq., is a courtesy title used by lawyers who are representing opposing clients to define and establish themselves as the hired counsel in the case in question. Lawyers typically use the title in written correspondence. The title "Esquire" is believed to have originated in medieval England to designate men who were of higher rank than a commoner but of lesser rank than a knight or a noble.