In my town, there are several food places that have come and exploded. The one that is most recent and beneficial to your cause is Moe's southwest grill.
Two years ago, Taco Bell was the hot spot in our town. Pretty much all highschool students went there all the time. Their business was great, the food was cheap, it was pretty much the meet here on a Friday night and everyone decieds where to go that night while they pregame. When we heard Moe's is moving in right across the street, we all thought it was a lost soul, bound to be overtaken by the reigning champ, TBell.
Moe's opened. Everyone, EVERYONE who worked during the after school shifts was a highschool student, generally of the more attractive sort. Do you want some attractive young person serving you, or do you want granny shaking as she grills your onions. Right. Everyone wanted to go try the place out, but mainly just get stoned, see their friends, and munch out. With the first meal, it was easy to notice that not only was the quality great, the portions were wonderful, a main course with drink was under 8 dollars. The drink machine was in the open, inviting free refills and every meal came with a free basket of chips. There is a salsa bar just after the register with several choices on types of salsa. VARIETY, each is delicious. People tend to overlook or take for granted these things, but variety and free things are important. 8 dollars is somewhat expensive for a highschool student when a TBell meal is half as much, so theres Moe's Monday. Drink + any burrito for 6 dollars. People loved Moe's, and at this cheapened price, every Monday was a holiday. Coupons were abundant and in every newspaper in town for good deals and the famous buy one get one free. Thats a half price meal. You're still making money, but people feel like they're getting a deal. PEOPLE LIKE FEELING LIKE THEY'RE GETTING A DEAL. It might decrease the earnings on those couple of burritos, but the benefits are endless. Not only did that bring more money conscious people in, it brought more people in general. When you're with a group of 6 people and theres two coupons, you just raked in more money and the two non-coupon people are going to go regardless of if they have a coupon or not. This fills more seats and makes it look like this place is booming with business. If everyone is there, it must be good right? I wana go there. You just got business of the non-locals who make decisions based on first impressions. The thought that you're eating at a place that isn't money hungry makes you more likely to return during a normal, full price, no coupon day and think nothing of it.
I forgot to include this above and don't want to reread the whole paragraph to find where it makes the most sense. Portions: Make portions good. People like being overfed. When your single meal fills you up completely, you are happy. When you can't even finish your free chips and are forced to give them to a friend/throw them away, you feel like you just got a great deal. Those chips are decently healthy, fill up stomach space, taste good, and cost maybe 10 cents max per person with 2 cups or salsa. People LOVE having to throw away food they couldn't even finish. Thats a happy customer.
Atmosphere: YongYong's is another nearby Chinese buffet that has nearly everything listed above, makes a decent business, and has good food. Buffets = eat as much as you can right? They must be packed 24/7. Nah, you walk in, its kinda poorly lit, the decorations look outdated even for China. The drab Chinese music isn't catchy. The seating is just tables and chairs. The cups are Styrofoam. DON'T DO THIS. BE ATTRACTIVE. Make your place well lit. Play the local hip-hop radio stations so everyone can listen to the top 20 over and over, thats what the general population likes! Get halfway decent cups and lids. Its something small that always bothers me. I hate foam cups. They suck and pollute the environment. WARM COLORS on the walls. Not super bright, just some earthy reds and oranges to keep it bright and cozy. Chairs and tables? Yes and no. Everyone likes booths much more than tables, face it, but you still need tables for those big groups, wheelchair people and people who just don't like booths. Glass. Use it where it looks good. People like glass, it looks modern and cool.
Something sick: Do something to stand out a little. For Moe's, it was their drink machine. I'll admit, I drove across town with a few friends just to get a soda once. They have some new high-tech soda machine with a touch screen and something like 150+ flavors. You step up to that thing and feel like you're overwhelmed with choices. I've had someone spectate and comment on my choices of sodas as they stood in line behind me. It was the lols.
Moe's now has lines to, or frequently, out the door nearly EVERY night. They make bank.
To go. This is completely off of the top of my head and probably already implemented somewhere. Your building has no drive thru? Damn. Make a line and register specifically made for to-go orders. When you're in a rush, you don't want to wait in a line for people who are eating in when you want to be in and out ASAP. Put a big sign above the beginning of the line saying "For the road" or something. Will some smartasses still go in that line and then eat in? Sure, but the majority won't because most people believe it or not will respect basic rules.
Theres my help. Hope I helped a little.