Hi Egret,
I don't actually have anything to answer at the moment, but I still wanted to say that it's a great question and I'll think about it.
I also wanted to link to the connected topic of How well do our parents know us.

It's a tough question that you ask. Some parents install spyware on their kids computers and other horrible such things to know what they're up to. Others hope that they raised them well enough until then that they will be ok, while always fearing other possibilities.
Perhaps the one thing I can say is that the only thing that seems important to me is to have him know that you're there for him any time he needs you. If he knows that, and he knows he has someone he can always turn to, that's probably the most one can do.

Egret, my heart goes out to you! 

Two things right off:  first I'm assuming you are a single Mom; second, how old is your son?  Let me try to tackle this from personal experience.  Between the ages of twelve/thirteen, as most psychologists can tell you, up to (possibly including) sixteen/seventeen, most normal intelligent teenagers go through something called individuation, to which you add raging hormones (both sexes) which is really not a way of driving parent(s) insane (though it is a temporary effect).  All of a sudden, on reaching that magical sixteen or seventeen, they turn back into truly amazing human beings.

As previously mentioned, I know very well what you are talking about, and not having a partner (particularly male, despite all the advances) has the double whammy: your need for moral, spiritual and emotional support (when you most need it), and his need for a balanced viewpoint, and of course the good old authoritarian deep voice.  In practical terms, again two things come to mind:  you need to remember that he is going through hell, pressure from both outside (peers, school, you - unwittingly, and inside, of physical, mental, emotional changes, not knowing who he really is, questioning authority, trying to discover a multitude of thoughts, feelings, where he stands in all this, and then of course, there is that dreaded SEX!!!  But trust me, I believe that is what makes great adults!

On hindsight, the best thing as Chris mentions (God bless that man!) is to be there, don't be judgemental, but do set reasonable limits, that is imperative.  My other suggestion is do not buy music because he likes it.  A conversation with my daughter (yes, you do live through it!) past purgatory taught me that among other things she wanted/needed things that were just hers.  She resented her friends talking to me, though she had no problem co-opting mine (which I not so secretly really like), listened to my favorite classical music in secret, put on the BGs when she heard me coming in from work because she knew it annoyed me no end.  She came out as the person I most admire and adore in this world. 

I hope this helped.

Thanks Chris for your response and for the link, I just browsed it and will go back to read again more carefully,  it's a very interesting discussion, especially many entries seemed to be from the view point  of the child, such experiences, either in novels or in life, are always of great interest to me as I don't have one of my own to draw upon, personally I didn't get to be parented at all from age 6-16, when both of my parents were mostly locked away in the labor camps. My lack of security or confidence during my own parenthood perhaps is a result of this. I often find myself anxiously seeking parental advice, sometimes to my own embarrassment.  Books help, but they are not interactive.

Jeanne Vanessa, thank you too for taking the time to share. I agree with your analysis on teenage development, the churning chemicals will finally settle down to a balanced level, hopefully! Sorry for not crediting my husband, who is as dedicated a parent as myself, and my boy has just turned 16, so we are about to make it to the end of the tunnel :-)!  Wouldn't it be easier if there were a switch to turn us from falling in love to falling out of love when the clock strikes TEEN, your child is simply your own heart placed outside of your body, while he is struggling to get away, letting go is really not easy! I don't expect him to ever be back to be the sweet little boy he was from year 0-13, in terms of evolutionary biology, there isn't any biological drive for our grown children to need to be attached to us, although the other way around is not true, we are programmed, like it or not, to reach immortality through our children, which is why their thriving is vital to us at all times! In a way, ultimately, our behavior is serving our own selfish interest. Realizing the biological bond with my child is going to be more and more of a one sided reality, I turned to humanity, hoping to create a bond through friendship that's mutual. Very soon it becomes obvious that love is not enough when it comes to cultivating friendship with a teenager, skills are necessary! And I'm far from equipped with the skill set to meet the challenge. I never needed to buy music for him but got copies of his music for myself, and his come from his friends. I read his books (of course only a small subset), learned to play some of his board games, eagerly attending all events that he is part of ... I turned down car pooling opportunities just so that I could chat with him, even if it's just for 10 minutes or so. Whatever I do, I couldn't seem to be able to knock open the door leading to his inner world, he is very private, very quiet, it might be his natural disposition, but what if it's not? He used to be the most talkative little boy I've seen!  What I care most is his sense of happiness, his psychological being as opposed to outward performances, come to think of it, there really is no correlation between intellectual achievements and psychological health, I'm always proud of his achievements, he is a highly educated young man, very well versed in classics, philosophy, science, a leading debater at school and nationally ranked math student... I could go on and on counting his achievements, which is why my husband is more than pleased with how his son has turned out to be, while attributing my anxiety to an excess of mothering hormone. I do believe that academic ability is only part of the brain story, there is the prefrontal cortex that's still developing until well into 20s, as a matter of fact, adolescence to young adulthood is the period that people are most prone to schizophrenia, for example. In short, he is not done with development yet, therefore I'm not ready to let go of him. At least he has commented that we are the most dedicated parents, he also expressed his wish for me to care less about him, I imagine him feeling too much parenting the same way as I felt there was too little when I was his age! So he understands we are always there for him, the only question for me is that whether or not we are there is of any value to him, it makes me so sad to think that as much as we want to be there for him, we are perhaps of no importance to him, and we are obviously not the ones whom he can confide with. Maybe all this will change, maybe one day we will talk to each other again, I'm waiting.