You're all set.
Your menu is decided. The space is decorated and ready for hungry diners. You are fully staffed and ready to take orders.
You need to do one more thing. You need to have your social media up and running. And not only that, it's needs to be fully ready to go. This means it's all branded in a uniform fashion. This means it needs to appear as fun, laid back and inviting.
This example obviously leans toward new restaurants. In this case, you are best set up to take advantage of the initial traffic. Your food will rock, your staff will be on point - patrons are going to want to follow you and mention you on social media. Make sure you are in position to capture that traffic and keep them engaged moving forward, bringing them back through your door.
For restaurants that are already up and running without social media, it's better late than never. Each day, new diners come through your door. That means that each day, you have a chance to capture repeat business and keep your fans engaged on a daily basis.
Facebook and Instagram are musts. It's good practice to be active on Twitter as well, even if you just connect it to your Facebook Page and duplicate the content to Twitter. In the dining space, Instagram is especially effective right now. Engagement rates are high on both standard posts and paid placements.
Yes, your restaurant needs social media. Whether you are opening tomorrow or have been serving people for 30 years, it needs to be a priority.