It's the most wonderful—and, yes, financially stressful—time of the year: With the holidays come tipping season in New York City. Whether you live in a fifth-floor rental walkup, a prewar co-op, or a luxe new condo, you probably have a list of people to thank this December. But first: Do you have to tip? If so, how much? And what happens if you don't? Brick Underground's founder and editors will guide you through the do's and don'ts of tipping; plus, hear from a Manhattan doorman what working in a NYC building is like during tipping season and throughout the year.