5. Watch the boozeIt's easy to have a few more drinks than normal at Christmas and while generally this isn't a problem, it can lead to more arguments.
Obviously you don't want to appear stingy, but limiting the alcohol intake of everyone should help reduce the number of booze-fuelled arguments.
6. If there's an argument...Try to separate the two people as quickly as possible and get them to take time out. Get them to accept the fact that no-one will win.
If they've been drinking there's no way they'll back down, so try to get them to act like adults and suggest they revisit the problem the following day when they've had a change to think about it and, hopefully, when they haven't had anything to drink.