All it takes is one slip up, one day a person is tired, stressed, exhausted or distracted and they will lose everything. Other times it's not even your fault. Unfortunately I have been in a building that burned down. In times like these you hopefully have friends or family to stay with.
Here are a few things to do after you know everyone is safe and sound but none of your things are.
1. Call the insurance company to get in touch with your adjuster.
2. Take photos, OF EVERYTHING! All damage. You'll need proof of claims.
3. Book a hotel room or stay at a relative's place for the week.
4. Keep all receipts from then on. So long as you're insured, you will be partially covered for all expenses.
5. Cancel/put on hold your phone service, cable etc.. with the exception of electricity for repairs (unless it's futile). If you can't use the service, why pay for it?
6. Keep your cellphone on you at all times because you'll get called for this, that and another.
7. Call your work, you probably can't come in the next day since you'll be busy with the emergency pack out.
8. Look for a furnished unit/condo asap because your home many not be livable for quite sometime. Insurance usually only covers so much (you must check with your adjuster), and you don't want a hotel bill eating into your budget.
9. If you have a laptop take it with you to the hotel, or family/friends place (since you will likely need to surf the web for info). If you are staying at a hotel, be sure to sign up for any point system, by the end of the stay it could mean a few free meals etc..
10. If you have a Swiss army knife or multi-tool take it with you, it will save hours of frustration spent hunting through your mountain of boxes.
11. Nothing is more painful than losing old photos, if you have a few that are salvageable remember that they can only be separated when wet. Don't try to peel them apart when dry, a trick I was told by a restoration company employee.