The number of menus and place cards at your wedding will be dictated in large part by the formality of your ceremony.
If you're having a casual, DIY kind of affair, it's fine to just leave a single menu on each table for multiple guests to share.
Every guest gets their own menu at formal weddings with fully serviced seated dinners, and place cards tell people where to sit regardless if you're dining on banquet tables or plastic patio furniture.
If you're looking to subtly shake up your table settings (and save a bit on dinner-related stationery costs), try combining the menus and place cards into a single document that lets your guests know both where to sit and what to eat.
Wedding menus typically give guests a choice of two or more dishes from which to choose as well as wine and beverage options. If there's a special story or romantic reason a dish is being served, a brief explanation may also be provided. Place cards list the names of the guests and their table numbers, and though they're usually left at the center of each place setting, they're sometimes found in unexpected places. Instead of placing cards on the table or on top of an empty plate, you may tie them to chairs, balloons, flowers or anything else.