There are several habits that you can get into with your teen that will help you notice if they are using alcohol or drugs, or notice if they are starting to get in trouble. One of the most basic ones is to have dinner together and make sure you are spending time with them, talking. That means, not having cell phones with text message conversations going on, not watching the TV or reading; but sitting down and talking to each other. Another thing is, before your teen goes out, you should know their friends. When they were little you did this, but as they get older, there is often a tendency of parents to let them go out with people that they don't know. Don't let them get into a car and take a ride with somebody who hasn't first talked to you about safe driving and seatbelts. It will make your teen embarrassed. It may make your teen annoyed with you, but it may also save their lives. Another thing that helps is when they come home, it's not acceptable to say, "Hey mom, I'm home," and go down to the basement or wherever and disappear. You want to make them come into the room and kiss you goodnight. The advantage of that is, you get to see them cross the room. You get to smell them. You can tell whether they have balance. You can see things, very unobtrusively, in the act of kissing them goodnight.