If a person faints or becomes unconscious, the first and foremost thing you should do is place the person in recovery position. It not only keeps the airways clear and open but also prevents choking. Here's a step by step procedure for recovery position.
Kneel at the side of the person lying unconscious. Check if the person is breathing.
Now, place the arm nearest you at a right angle to their body with their hand upwards, towards the head.
Tuck the other hand (left hand in this pic) in the gap between the head and the neck. As you do so, make sure the back of the hand is touching the cheeks.
The next step is to bend the knee farthest from you to a right angle.
Now, roll the person to one side, preferably (right side as seen in the pic) by puling the bent knee. Make sure that the top arm is supporting the head.
This is the recovery position. Stay with the person till any medical help arrives and monitor the changes.