first thing,you have to visit there early as possible.remember to bring your original passport and receipt printed at the moment you paid the on line amount for your medical (100QR i guess)5am is better.after the security will escort you into one large tent.there will be thousands of thousands workers and you have to bear the smell of those guys as I did.so you have to wait until ur turn,
after the security will give you one number and escort you to one room where your passport and receipt will check.