According to Stanley M. Zildo as quoted from his book 'First Aid, First Aid and How to Correct Handling of Emergency', fainting can be prevented by the victim lay and lift legs as high as 15-25 cm. It could also be seated with your head touching your knees bent.
However, if the fainting has occurred, it can be done the following things:
1. Lay the victim, lift legs as high as 15-25 cm although there is the possibility of head injured.
2. Open the airway, perform artificial respiratory if necessary.
3. Open the clothing, especially around the neck of the victim.
4. If the victim vomits, tilt or turn his head to prevent choking.
5. Slowly, rub his face with cold water and do not splashed onto the face of the victim.
6. Check back over the body to see if there is swelling or deformation caused by a fall.
7. Do not be drinking even though the victim is recovered.
8. If medical care is not successful within a few minutes, take the victim to a doctor or paramedic.