Checklist for leaving the US

Hey there!
Relocating to Denmark in a few months for a great opportunity. The relocation company has been very thorough and comprehensive with everything I and my family need to do to move to Denmark (immigration, language lessons, moving, etc) but I find that I need some guidance on everything I need to do or should do when leaving the US.

For instance: getting out of apartment or car leases; other things I am not even thinking about…

Any suggestions? Advice? Resources?