To start off with, answer these questions: What kind of clients do you cater to? Are they upscale execs, working people, students, suburban moms? The answer to this question will help you consider the right menu/products options. Is your location a natural spot that your best clients pass by every day? What is the parking situation like? The answers to these questions will help you understand your normal traffic patterns and if you have a hope of surviving in your current location. What are your expenses? Are you carefully seeking out cost-effective vendors for plates, utensils, foodstuffs, etc? Making some adjustments here could help to improve your bottom line.
Next, do an in-house survey. Ask your customers what papers they read, what local radio stations they listen to, what other products or menu items they'd like to see you carry. Once you have answered all these questions, you'll have a better idea of whether introducing the right mix odd new products or services (delivery to local companies, catering, fancy or health-conscious foods like wraps and unusual salads, drinks, Odwalla bars or organic drinks) or some combination thereof will generate the income you need to thrive (not just survive).
If your location and parking situation is fine, I'd suggest you meet with a local banker or economic development officer, to look into getting an influx of cash to meet your ad campaign, income and product expenses. At the same time try some guerrilla marketing tactics: Send out emails to local businesses, schools, and Chambers of Commerce about your assorted offerings and daily specials. Start actively encouraging your current customers to spread the word about how great your place is. Have a professional graphic designer make up a 8.5 x 11 sales "poster" using your logo, that you can fax to area businesses every day. Send a professionally written press release to your local daily and weekly papers and cable channels - they are always looking for great new places to recommend to their readers and viewers.
Best of luck!