Burger King Corp., a company clearly in search of an advertising image, has returned to its oldest but most effective one: flame broiling. Beginning Feb. 29, the Miami-based company will launch a $200-million, year-long series of ads that focus on its claim to flame. The ads, created by the New York ad firm, N. W. Ayer, include a new jingle and slogan: "We do it like you'd do it." Burger King also said it will launch a series of ads pegged for black customers that feature Kadeem Hardison, who stars as Duane Wayne on the television show, "A Different World." In the advertisements, Hardison--ever the ladies' man--tries to impress the women by buying his hamburgers at Burger King instead of cooking them on his backyard grill.