When I was a teenager my boyfriends parents were always around. We were in the band and they were at every competition. We had lots of friends and when we looked for places to hang out they would always offer to order pizza at their house. When we got a little bit older they bought a used pool table and always had cold drinks. Even better, they were usually around. They always suggested things for us to do (one of them would offer to drive us to the video store to rent a video, or they would offer to take us all to the lake etc) When I was a kid I just thought they were "cool"....but as I got older I realised that they were enticing us to include them in what we did. I'm 28 now and I and their son have gone our seperate ways, but whenever I visit my parents, I visit his too. I'm thankful that they had the insight to do that.
That was a stark contrast to my parents. My parents believed that their home should always be a place of calm and serenity. Friends shouldn't be invited over. You could NEVER have a mess. And conversations about life never happened. We ate dinner together, but we never brought up any topics that were difficult to talk about. To this day I don't tell my parents who I'm dating or what we do unless it's pertinant. My brother and I always joke that the first time our parents meet our wives/husbands is probably going to be our wedding day.
Point is....it's a fine line to walk, but make your daughter and her friends feel safe and welcomed in your home. Tell her things that you like about the guys she chooses. (Like - tell her that you thought he was very nice and polite...or that your really impressed that he gets good grades...or that he's got great tastes in movies) that will make her want your approval and it will also make her feel ok about coming to you talking about what she likes as well. As for not smothering her...open a conversation with something easy for her to answer (like - what's her boyfriend's favorite subject or something else that is rather impertinant) and let her take the lead. Girls talk and if you just give her the opportunity then she will talk to you. And let her decide when the conversation is over too. Tell her about your boyfriends. Tell her the things that you like and admire in her father/ your husband. Just don't tell her all at once.
You do, however, need to have certain information from her...like...what his phone number is, what his parent's number is. Where they are going, who else will be there etc. She'll hate that....but...she's less likely to get in trouble if she feels like everyone is checking up on her.
There is, also, NO WAY she can date without you telling her your views on boundries. If you avoid this conversation then guaranteed she won't know what is right or wrong.
The best way to open the door for safe dating.....your daughter is 15 so she can't drive. Offer to drive them. You'll get to overhear what they are doing, what they are talking about and you'll know where everyone lives.
Good luck to you and your daughter.