Paul informs us that it's better not to have sex at all, but if you must, for god's sake don't fornicate and stay heterosexually monogamous. Also, you have to have sex unless it's prayer time, but then you have to do it again right away lest Satan tempt you. Amazingly, you can still choose the position yourself.
He would actually prefer it if we were all celibate like him, especially widows. But he realises it's quite hard to do, and after all, it is better to marry than to burn (v. 9).
On to divorce: women can leave their husbands, but if one does, she can't remarry anyone except the original version. And yet, no one is calling for us to enforce this particular bit of biblically-mandated claptrap, even though it's in the same chapter that would seem to preclude gay marriage or sister wives.
Mixed marriages: they're fine. The resulting spawn are christians. However, if your unbelieving spouse leaves, NBD.
Be content with your lot in life. Don't get uncircumcised if you are (Yes, it's a thing) and don't get circumcised if you aren't. If you're a slave, don't sweat it, but take your freedom if it comes available. Unbelievably, this will still be a thing in 2012 that multiple candidates for office will still be saying.
Virgins: god hasn't said much, but Paul has an opinion, which is that it is a good thing to be. If you're married, fine, stay that way, but if you aren't, stay that way, too. If you must, it's fine, but it will cause you a lot of heartache in life. Also, the world is ending soon.
Finally, he get's down to the brass tacks: being married makes you think of worldly things, like how to please your spouse, but staying single means you can focus on god. Hah! If a woman is getting on in years, it's fine to marry her, but better not to. And if her husband dies, she can't remarry anyone except a fellow christian.
Knowledge is bad, charity is good. If you think you know something, you don't. If you love god, he'll love you. It's fine to eat animals sacrificed to other gods, but try not to do it in front of people of weak faith lest they sin. Being a vegetarian is also fine.