>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.