Most of the time, you must stop your contracts (water, electricity,
telephone, rent, TV etc) by sending a letter. If you paid your bills by
standing order, don't forget to tell your bank.
As you needed to complete forms when you left, you will need to fill in
forms when you return. The easiest way is to contact the consulate where you
are registered to sort out your situation. You will have to establish a fully detailed inventory of your furniture. A moving form attestation is often demanded when you
pass the border (you can ask for it at your Consulate).
You will have to think about school registration
if you have children.