With the advent of social media, I don't think marketing a product, such as restaurant could be that hard. It all depends on how unique the food is with regard to all other foods in the area.
There's this newly established burger restaurant near our place that's attracting a lot of customers. What they did is to name their products according to people's emotions. Hence, almost all of their products get a fair amount of sales. Moreover, during their 1st year anniversary, they decided to sell their burgers for only a penny each. And they did this again during their 7th anniversary. With these type of promotions, it's like give free tastes but you somehow earn and get to attract more people through word-of-mouth.
The key is to carefully strategize your plans on advertising based on the current trend.