First, the do's: Pick a time that's good for both of you, when neither of you is running out the door. To avoid interruptions, you can choose a place in the house where you'll have privacy and let your teenager see you unplugging the phone or turning off your cell phone. This signals to your teen: "You're important and there's no one I'd rather speak with right now." Other ways to demonstrate to your teenagers that you're interested in what they have to say is stopping whatever you're doing (computer work, dishes, balancing your checkbook) while you listen. Alternatively, you can go for a drive together or take a walk away from the rest of the family and other distractions.
You can start by sharing your feelings about an incident that happened at work (not related to your teen, but just as a conversation opener) or one that happened to you when you were a teenager, which might have a bearing on what your teen is presently going through. Give your teenager a turn to share his or her opinion, to disagree with what you said, or to bring up another issue. Now, this is the harder part: Work on becoming an Olympic-class listener. You don't have to jump in with advice, moralizing, or rebuke. Just listen and let your teenager feel heard and really understood. Once you've heard your teen out, take another minute or two to think about these revelations, and only then explain your way of viewing the situation or tell your teen you'll have to do some research and get back to him or her.
And now for how NOT to communicate with teenagers: Don't make fun of what they tell you, lose control and start yelling, or react in a horrified way. These are great ways to not only get your teenager to storm out of the room but to decide next time that there's no use talking to parents. Treat teens with respect and patience and the lines of communication will hopefully stay open.