1. GIVE your teenager reasons: You don't have to have a long list of reasons as to why you say no to something they want or ask for. But I think it's a bad, actually lazy habit to get into to NOT give them a reason. I mean there is a reason you are are saying no after all, right? Any person can say, "Because I said so, I'm the parent, that's good enough." Why not shoot for something that will work better and be more loving? Show your kid that they are worth it.
It's a step toward respect if you can take just literally an extra minute or two to give them a good reason. They will appreciate it. And not only will you be respecting them to care enough to give them a good reason, but they will respect you--AHH BONUS!
2. Ask them questions: By this I mean, don't assume. If you are in a situation with your teen where they did something wrong, or even if you think they are hiding something--go ahead and ask them. Inquire about their lives in a non accusatory way. I've caught myself plenty of times coming across to my daughter that I know what she did, or I assume why she did it. When I find myself in a situation with her where I'm disappointed or suspicious I've learned to ask questions. That way it's more of a two way street and I'm not just shootin off my mouth trying to control a situation that might not even be a reality. I've found most times than not that when I do ask her about stuff, she appreciates it, and will answer. It shows her I respect her because I'm addressing an issue without assuming or judging.
3. Give them a voice: I believe our kids want to be heard. And in a desperate way. They have got to have an outlet--a place they can share what they are feeling. Being a teen is so difficult because of the emotions that are so rampant in their lives. I remember them very clearly even as an adult now. We can respect our kids by giving them a voice in many different situations: if they get in trouble, we need to let them share about their thought process a bit, or when they get frustrated or annoyed with us, we need to let them say why. We need to hear them out if they feel that something we do is unfair, rude, or embarrassing. This creates a mutual respect because it gives them a chance to experience us as human beings, not just parents. It helps anyone to be able to speak up and work through feelings, doesn't it? Listen to what they have to say.