What should i know about my teen?

What is meant by "adolescence identity crisis" Do young people today become sexually active too soon ? Should we take it for granted that our teen knows about adequate sexual protection ? What can we do if our teen becomes pregnant ? Can we help our teens recover their motivation at school ? If, so, how ? Is it normal for our teenager to spend a lot of time at the computer ? Is there anyting we can do if we don't like our teenager's group of friends ? In case of parental separation, is it preferable for teens to live with one parent rather than the other ? What are we to think of the tattoo and body-piercing trends that have been adopted by so many teens ? Some teenagers suffer from anxiety or depression. What exactly does this mean ? What can we do to help ? ... and many other questions !