First, chat about their professional image, including work space organization and personal appearance. This way, when you raise the delicate issue of table manners, it’ll be part of the bigger picture.
When you get into specifics:
1. Speak from experience rather than giving a “you-need-to-improve” lecture. Say, “You know, I’ve found from years of business lunches that there’s a secret to winning over clients. It has to do with pacing. You need to do everything more slowly than you normally would, like eating, chewing, even talking. It really works.”
2. Hand out articles on “the little nuances” of a business lunch, like what to do with your napkin when you get a midmeal phone call. (Answer: If the napkin is soiled, leave it on your chair.) Scan books and workshops on for pointers.
3. During your next business meal, wait for a private moment when only your messy colleague is at the table. Then say gently, “No need to rush.” Say it casually, and continue with your half of the conversation. Don’t make a big deal about it.