NEW YORK (AP) — Wal-Mart Stores Inc. needs to spell out in its first press conference this week how it is dealing with issues that continue to dog it, from sex discrimination to wage and hour violations, image consultants say. "They need to persuade people they are bigger than people's attitudes toward them," said Clarke Caywood, professor of public relations at Northwestern University in Evanston, Ill. What's important is for the world's largest retailer to provide specifics about how it will execute better business practices, Mr. Caywood and other image professionals say.