Know their friends and the other adults in their lives.
Expect them to tell you where they are going and with whom, but make a conscious effort to get to know their friends and what interests they have.
Find a balance in the way you express interest in what they are doing, without “policing” them.
Spend time with them, and see what they are watching on TV and listen to the music they are listening to.
You may limit computer use to common areas in the home, but also educate yourself about what they are doing online.
Talking with them about what is important to them might help you to build trust and let them know that you value their opinions.