[user104658]

Originally Posted by Angelika

Its better to keep them talking and constantly compromising with parents on what they want to do. This isn't a foolproof solution but its better than constantly telling them "no."

Completely agree with this; people have it totally the wrong way round. Teenagers don't need more rules, restrictions and supervising... that's what LETS things like this happen. When you impose strict limits like that on a teenager, they will simply clam up, and find a way to sneak around without you knowing what they're doing. They won't trust you to give them any freedom or to understand them and so they will simply hide certain things - like strange new online friends - from you and then they will sneak off to meet them without telling anyone where they're going.

Instead, if you GIVE them that trust and freedom, if you treat them more like an equal, if YOU tell THEM what's going on in your life as you would a friend rather than a subordinate, then they are MUCH more likely to voluntarily tell you what's going on in their life. And if they're telling you about these things, then it's much easier to spot when something dodgy is going on that needs to addressed.