The techniques of artificial ventilation without equipment are two in number, they are: word-of-mouth and mouth-to-nose. Both techniques are equally effective. They allow the victim to breathe the air exhaled by the rescuer (this air contains enough oxygen to make these techniques effective).
There is also a variant of these techniques, which is the mouth-to-mouth-and nose-and that applies to infants.
The method chosen will be effective only if the airway of the victim and are still free and if you run movements deliberately, with a frequency slower than your own breathing.