What to pay extra attention to on the day of departure for a long stay abroad?

On the day of packing or loading, reserve a clear place or closet for items that the mover must not touch. Think of that bag with important documents, medicines, your children's favorite stuffed animals: without a good overview, there is a chance that these too -for days or weeks- will end up in the moving van.
Call the planning department in advance (1-2 business days) before the move for start times.
Take down last remaining curtains.
Walk around the house immediately after the movers arrive and make notes on final action or attention points.
Walk a last-check lap around the house after the moving truck is loaded.
Take meter readings and disconnect gas and electricity (if a new tenant is not moving in or not immediately).
Drain the water supply in the winter (even if it is not freezing).
Lock all windows and doors securely; hand keys to caretaker/new tenants.
Say goodbye to neighbors, family and friends.
Agree on an indicative time when you will let the home front know that you have arrived; point out once again that there may be time differences and mention that during the trip something may happen as a result of which you will temporarily be unavailable or less accessible, be delayed, etc.
When you are emigrating with children, where possible discuss the course of the travel and arrival days again, so that they know what is most likely going to happen. As always when traveling with children, make arrangements about what to do if someone gets lost or lost (who to talk to, meeting point at the airport, etc.).
Despite all the emotions surrounding the actual departure: try to make sure that the "last memory before departure" is a positive one, one with a smile; that will make it a little easier for those left behind.