Break The Ice
Mingling is an art, but it's not hard to learn. First, allow your host to make some introductions, and if someone looks slightly familiar, say "nice to see you" rather than "meet you." Even if you actually haven't met before, it's better than committing the "I don't remember you" faux pas. Also, always be on alert for the double-kiss when you go in to greet someone - they really can come out of nowhere.
When striking up a conversation with someone new, try to start with something other than "What do you do?" Make things interesting! Ask about their latest travels, their holiday plans, or, of course, what they thought about the season finale of The White Lotus.
[Photo via @carodaur]