Social distancing is key to keeping customers and employees safe. And, it's basically impossible to keep customers six feet away from each other if every table is open.Most restaurants are marking certain tables off-limits. Others are simply removing some of the tables from the restaurant. If every table is open and the restaurant has as many seats as it did before the pandemic, you should avoid this spot. While blocking off some tables can help promote social distancing, you should be aware of any crowding throughout the restaurant. If people are crowded around a bar to order drinks, avoid that part of the restaurant — or avoid the restaurant entirely. An airy restaurant, with big open windows and fans, is safer than a spot with poor airflow that relies on air conditioning to keep customers cool in a stuffy room. In an early research letter published in the journal Emerging Infectious Diseases in April, researchers examined how the coronavirus spread among nine people eating at a restaurant in China in January. According to researchers, the restaurant's air conditioner blew the viral droplets of one person who was asymptomatic farther than they might have normally gone. Researchers recommended increasing the distance between tables and improving ventilation to prevent the spread of the coronavirus in restaurants. Or, even better, pick a restaurant with outdoor seating.The National Restaurant Association has offered extensive guidance on cleaning and sanitizing, as well as general advice on how restaurants can reopen relatively safely. It is hard to tell at first glance how closely restaurants are following guidelines. If you're concerned, it is worth calling ahead of time and asking what new policies have been rolled out to keep customers and workers safe. Ideally, everyone would wear a mask when people are inside or within six feet of each other. However, that's difficult to do while you're eating. Restaurants should require employees to wear masks. In kitchens, it can be hard to strictly enforce social distancing, and waiters are typically forced to come in contact with customers when they're serving food. Workers wearing masks can also indicate if the restaurant is taking other safety measures seriously. It is hard to tell just how carefully workers are following sanitizing policies, but it's immediately clear if people are wearing masks. Limited tables and social distancing measures mean that fewer people will be allowed into a restaurant at a time. While employees can turn customers away at the door, a more convenient way to impose limits is by requiring reservations. I think a lot more of the places that used to just be relying on walk-ins are going to have to start actively managing the restaurants, and they are going to use our software to do so, Steve Hafner, the CEO of OpenTable and Kayak, told Business Insider's Gloria Dawson.You don't need to count out all restaurants that allow walk-in customers. But, making a reservation can ensure you're visiting a restaurant that is following guidelines on how many customers should be allowed inside — and avoid the disappointment of being turned away. The White House's guidelines for reopening say that states need to see 14 days of declining COVID-19 symptoms and cases (or a decrease in the percentage of positive tests within that time frame) before reopening businesses. Hospitals must able to treat all patients without crisis care and have a robust testing process available for workers.If you live in an area where the number of COVID-19 cases is still increasing and hospitals are struggling to provide care for patients, it may not be safe to return to restaurants, even if dining rooms are open.