Don't let guests mix their own drinks. Never force a drink on a guest. Close the bar 90 minutes before the party ends and serve a dessert treat with coffee. Remember, only time sobers someone who has been drinking. If, despite your efforts, some of your guests have had too much to drink, drive them home, arrange for a ride with another guest who is sober, call a taxi, or invite them to stay over.
Coffee can sober up someone who has had too much to drink.
It takes about one hour to metabolize each drink. Hard liquor is more intoxicating than beer or wine. Someone who has had too much to drink will look intoxicated. One drink can impair someone's ability to drive. Judgment is the first thing affected when someone has been drinking and important motor skills are next.