If somebody does something like slit their wrists or takes a bunch of pills, it is probably just a cry for help as those are known to be non-lethal much of the time, and anybody who actually wants to die would take the time to do some research on the best way to die. So if you survive, odds are you weren't really trying to die; you weren't putting enough heart into it. Blowing your head off with a shotgun, hanging yourself, or using the suicide bag method are relatively good ways to make sure you die. The latter is the least painful/least scary/most peaceful, and therefore highly recommended.