Big name event and wedding planner Mindy Weiss has overseen the elegant and extravagant nuptials of stars Ellen DeGeneres, Gwen Stefani, and Hilary Duff. Brides-to-be will have the opportunity to meet Weiss as she signs copies of her new book, “The Wedding Planner & Organizer,’’ at David’s Bridal in Danvers on Feb. 2. Until then, here’s a sample of her expert advice for keeping costs down on the big day.