The person greeting you from the threshold can make the whole room feel easier to enter.

Arriving is the hardest thirty seconds of any gathering. You come in without knowing where to stand, who is here, or whether you are early. One person coming to the door dissolves all of that at once, because you now have somewhere to be and someone to be with while you find your feet. It costs them almost nothing and it saves the other person an hour of quiet effort.

At the next thing you host or attend, watch the door. Meeting one arrival and walking them into a conversation is the most useful thing you will do all evening.