>1. If this is a dinner party (or people are all seated), force people to get up and move in a way that they'll meet new people. Do this when you're about 2/3 of the way through the party.
Better, I've found, for compelling people to interact with others they may not know, is to assign seats. This enables separating couples or others with a preexisting connection. The act of eating offers the benefits of a subject to discuss (if needed) and makes it so it's acceptable to periodically look away from the conversation partner. Just note that depending on the size/shape of the dinner table, it may be necessary to think about who people will be seated adjacent to and seated across from.
It used to be custom (in high society, not anywhere I have dimmed) to sit boy girl boy girl, and for ladies to talk to the man in their left during the first course, right during second... to keep a balanced conversation going
When arranging seating for a dinner (not that often), we tend to separate couples. And when at someone's house when there is not pre-arranged seating, my wife and I tend to sit apart.
Stendhal thought that the 19th Century French custom that married couples should attend the same gatherings had harmed the quality of conversation. I think he said this of the Empire.
Better, I've found, for compelling people to interact with others they may not know, is to assign seats. This enables separating couples or others with a preexisting connection. The act of eating offers the benefits of a subject to discuss (if needed) and makes it so it's acceptable to periodically look away from the conversation partner. Just note that depending on the size/shape of the dinner table, it may be necessary to think about who people will be seated adjacent to and seated across from.