1) NOC in arabic from your sponsor / Company for buying a car.
2) copy of your qatari ID
3) Copy of Qatar ID of the person whom your going to buy
4) Mulkia (Registration ID)of car
5) Insurance copy & orginal of the car
6) your credit/atm card for making payments at the counter. it cost around 200 or 300
7) Aarabic letter of transfer that you get typed out from typists any where or sitting around the traffic Dept's office for a small fee ( say QR10/-)
8) This you can do this over conter in city centre also
9) The person selling car should also be with you

The actual transfer takes about 10 minutes at the counter and you get your card of registration on your name.