I almost left the country last year, but I did go through the checklist,

1. Close ALL your credit cards issued from Qatari banks, then close all your banks accounts in Qatar. Transfer your money outside Qatar, and if there is more payments before you leave, work with it in cash form
2. Advertise your car and furniture for sale. You may continue using many things including your car, by agreement with the buyers. For the car, if you own it, ask for a cash deposit and agree with the seller to transfer 2 days before you leave. If there is a loan on the car, it takes longer to transfer, but you can work it out with the buyer as well.
3. Ask for many papers from your employer, certificate of employment, NOC even if you do not need it, recommendations letters, etc
4. Inform the house owner that you are leaving, in writing, and have them sign and date. Work with Qtel and Kahrama on closing the accounts, and the dates of stopping service.
5. Get copies of schools records for your children, for all the years they studied here
6. You can get a letter from CID office, saying that you did not do any crimes while you lived in Qatar
7. Reserve airline tickets, and arrange with your sponser on terms of payment. Avoid using Qatary credit cards to pay for the tickets.
8. If there was any health problems, get copies of reports from clinics and doctors
9. Keep RP cancelation until last, as you may decide to stay more days at the end for whateve reason
10. No worry, I am sure few friends will be happy to help if you need things from Doha after you leave.

Best wishes.