Grumpy security agents, the threat of flight delays, crowds massing at the gate: Together, they’re a recipe for traveler stress. If you have access, airport lounges can be a serene haven in which to counter it. Lounges have become easier to access and, at times, overcrowded.

As airports open more of them, travelers should recognize the major do’s and don’ts. For fliers entering a lounge for the first (or 500th) time, here’s our etiquette guide to keeping the peace within the club. You’ve strolled into the lounge, and the doors to your airport retreat close behind you.

Now, only one person separates you from the breakfast buffet and a preflight mimosa: the lounge agent. "Be courteous to the people who are checking you in, much like flight attendants on a plane,” said Diane Gottsman, an international etiquette expert and founder of the Protocol School of Texas. Don’t just assume you have entry.

One lounge may be accessible with the right credit card, while another lounge next door could be restricted to certain premium passengers. Figure out which lounge you have access to arriving at the airport. A bonus: If you have multiple lounge options, a little research can tell you in advance which has the better champagne (or soften the disappointment if they don’t have any).

Typically, airport lounges are shared public spaces. If a lounge is particularly popular, that might even mean a line to get in. Gottsman said that as with any public domain, there should be certai.