DannyUndead Suicide
abuse (emotional, physical, sexual)
pregnancy and sex
sexually transmitted disease
drugs
bullying
physical health
eating disorders
relationships with friends, family and others
their future
the possibility of earning money
being overworked at school
school marks
appearances and clothes
participating in youth movements

I think, at first we have to pay attention for emotional state of person. There are so many situations, when people face with different difficulties in life, and they can be very vulnerable for person. For example, death of his parent or friends. Not everyone can handle it. We must help people, who feel very bad because of their sorrow. 
Then, we have to protect teenagers from pregnancy and sexually transmitted diseases. Because early pregnancy or AIDS will ruin their life and they will regret about it the whole life.
Also, we have to protect them from bullying and using drugs. They have to focus on their health, because they will die cause of drugs. 
They have to think about their future. They have to study hard for best life and work.