dogloverjb is correct you will have to go to the DOH arrival terminal and go through customs. You will need to pay QR100 (~$27.50) for a 30 day visitor visa paid using a credit card. Then you will need to take a cab to the departure terminal, separate building, ~2 km away and go through normal security and what not there. Not exactly the most fun airport in the world and unfortunately the new airport has been plagued with delays and doesn't seem to be opening anytime soon. Hope this helps. I am currently in Qatar for work.