I have recently been watching a lot of "Top Chef" and "Hell's Kitchen." I agree with the first answer's hints on thesis statements. I'd like to add some help in the area of exactly what you should say, when it comes to writing about a restaurant.
Every episode of "Top Chef" starts with a quickfire challenge - and a guest judge, typically a very famous chef from a successful restaurant, walks around to each player and asks, "What do we have here? And what is the concept behind this?" It is the same thing in the bigger challenges. The two most important questions when opening a restaurant are "What kind of food are you going to serve?" and "What is the overall concept of your restaurant?"
For some, the inspiration comes from a certain culture (ie: Indian food). For others, it is the attempt to do something that hasn't been done before with food that everyone loves. I've repeatedly heard this is referred to as "New American food." Whatever your concept is (and it doesn't really matter) for your entire restaurant must be the common idea that ties together your food, your decore, your prices, your customer base, even your location. Come up with a concept by asking, What am I inspired by? What do I want to serve? Who do I want to market my restaurant to and why?. Make this your thesis.
What your thesis statement will be depends a great deal on what kind of paper you are writing. Your thesis should provide the direction to your paper. What are you going to talk about? What are you going to try and show or prove? It should set the stage for the rest of your paper. Think of it as the opening act to a play. The narrator comes on stage and says his monologue preparing the audience for what they are about to see. Your introductory paragraph is that opening monologue, and your thesis is the last line you say before you walk off stage, the curtain opens, and the show begins. It should grip your audience, and leave them wanting more. It is not merely a simple statement, but a precursor of the questions you are about to answer. A good thesis statement makes it impossible for a person to put the paper down until they've made it to the end.
So, what are you trying to say about your restaurant? Is it something new that has never been done before? Is it a spin on something that you wanted to improve? Do you have a specific type of cuisine people have never tried cooked how you do it? Jot down some notes about what you are going to tell your audience about your restaurant, and think of how you could say it in a sentence without giving away how you plan to achieve it ;)