Initial treatment for nose bleed is to keep the individual in an upright position, which leads to relatively decreased blood pressure in the nasal vessels (compared to lying down.) Leaning forward is very important, as this helps to prevent swallowing blood, and can aid in blood clot formation.
Bleeding can be controlled by direct pressure, and in this case, pressure can be applied to the outside of both nostrils, as close to the nasal bones and face as possible. Pressure should be firm and constant. Generally, pressure should be applied for 10 minutes (by the clock is best, because in this position, only 2 minutes can seem like 10!) This will control the bleeding in almost all cases. If bleeding is controlled, the victim should avoid blowing their nose for 24 hours, as this may blow out the clot that has formed to stop the bleeding. Often, healthcare providers recommend an Afrin type nasal spray for a few days to help constrict the vessels of the nose and prevent re-bleed.
Bleeding that can not be controlled with 10 minutes of direct pressure generally needs to be seen urgently by a healthcare professional, as the nose may need to be packed for a few days with a gauze type pad in order to stop the bleeding and prevent re-occurrence. Pressure should continue to be applied in the meantime.