Thank them for their time, ask for forgiveness, empathize with their situation, offer a solution, invite them to continue discussing in private. One thing you'll see happen with inexperienced business owners is that they'll try to publicly respond to every negative review. While this is absolutely something I highly recommend, there are some important caveats to keep in mind. So buckle up and grab a pen and a notebook because this will be a small, fairly detailed item.
The best-case scenario is that your brand actually grows, but this depends on you handling the situation tactfully. A carefully thought-out response, along with clear efforts to fix the problem, can show customers that you really care what they think, and that's always a good thing. Don't post a negative comment about something like food that came out cold, an overcooked steak, or a flat glass of prosecco without first trying to discuss it with the staff. That way, your review won't reflect the typical experience someone might expect to have at that restaurant, so it's against the purpose of writing a review in the first place.
Whether it's a five-star Google review for a new coffee shop or a one-star Yelp rating for a neighborhood restaurant that's gone to hell with a new direction, chances are you've published at least one review of a restaurant online throughout your career on the Internet (and probably will again). However, if you notice an issue where several critics say that your food costs too much or that it doesn't offer a price equal to the price, it's not a bad idea to check your prices. And responding directly to the reviewer by name reminds them that, in fact, there is a human on the other side of this review. If just one bad review about a restaurant says that your food is too expensive, you may have only had one guest with little money.
Also, don't write a review about a place you went to a year ago just to increase your number of reviews looking for some kind of imaginary influence on the Internet.