Best way to promote a new restaurant online?

I'm working on starting a restaurant and now sure where to begin to generate exposure online when it opens.

Yelp works once you already have a few reviews.

What are some other ways to get the word out to ensure the business doesn't suffer from an empty seats problem (new customers would see an empty restaurant and presume it's not good since it isn't crowded)?

Creating online buzz "when it opens" is too late. You need to get the buzz going long before opening day. It takes time to build up an audience.

A lot of this depends on your target market, but assuming locals, who are a bit like your social/family circles:

Facebook events:

- Pre-opening tasting event
- Private Opening night, invite your friends and family.
- Grand Opening, ask your friends and family to help you share the event to their friends.

Great content:

Use Instagram to build some easy Twitter/Facebook content:

- Photos of the building phase.
- Sneak peak photos of the upcoming menu.
- Photos of great food during the "testing" phases.
- Share some recipes or tips.

In Facebook, add additional running commentary to describe what's in the photo. Using local ingredients? Tell that story. Doing something special? Tell that story.

- Ride on the wave of other interesting content. During the so called "Blue Monday", I created some content for a couple of companies that when shared with the appropriate hashtag, reached far more people than usual. Not necessarily the right people, but that's life with internet marketing for free.

If you must, create a "like and win" type post for people to share - but don't do this too often (because it get's old, fast).

Advertising:

If you have some money, you can use Facebook to advertise to a frighteningly specific audience. For example: "People between the age of [target ages], who live in [my city] and liked [name of biggest competitor]".

Don't forget offline too:

Offline marketing is also valuable. Think about what you're doing to catch the people walking by the restaurant before (and after) it opens. Think about how to engage with the businesses around the restaurant - and not just "how will you advertise my restaurant", but "what can we do to help each other".

Find a local cause or event in the neighborhood where the restaurant is in, and partner with them to drive awareness.