Choose a menu you can mostly finish early
A braise, a ragù, a sheet-pan dinner. Anything that improves by sitting. One thing cooked to order at most, and ideally nothing.
An appetizer that is assembled rather than cooked — good cheese out of the fridge an hour early, bread warmed, olives with orange peel — buys you the entire first half hour.
Three mistakes
Cooking something new. Do not test a recipe on guests; cook the thing you have made before.
Too many courses. Three is generous. Four means you are in the kitchen.
Starting the food when people arrive. Have the first thing on the table before the doorbell, so the evening opens with you pouring a drink rather than apologizing.
