Neil Rosenblum, owner of three Manhattan Pet Stop stores, has found a way to publicize his staff's expertise. At the company's Upper East Side location, employees have begun posting a sandwich-board sign that displays a pet-care "Tip of the Day" outside the store to catch the attention of passersby. The tips have ranged from advice about how often to feed your pet to a recipe for a remedy for skunk scent. The Pet Stop began posting the tips in mid-1997. So far, the company has been able to rely on the collective knowledge of its 15 employees to generate tips.