Discussions

I need some advice from any parents who have been through this. My teenager (15)is a slob. His bedroom and bathroom are a disaster. Clothes all over the floor, garbage, dishes etc. I'm sure you know what I am getting at.  
 
So my question is this. What do I do about it? I have nagged over and over and it doesn't seem to help. Do I just let him be and if he has to wear dirty clothes to school and work then so be it. When he has his friends over, hopefully he will be embarrassed by the mess. He also has a girlfriend so I'm sure he will want to be wearing clean clothes when he sees her.  
 
Also...homework. Do I ask him every night if he has or has done his homework or do I just hope that he is going to be responsible enough to do it.  
 
I don't want to nag too much and have him totally shut me out from everything.  
 
Ah, the teenage years!!  
 
Thanks