Obviously it is a very complicated issue and question your asking here. But to boil it down to it's simplest form right is anything that promotes life and happiness. Wrong is anything that promotes the opposite. Independence is superior to slavery (accept when it interferes with the previous rule)
Stealing is wrong for several reasons. One is that you are dependent on another, you have offered nothing and earned nothing. It is also wrong because it promotes (and often uses outright) violence ergo destruction.
If it feels good (and hurts no one or no one but yourself) do it. The thing here is that we must always consider how it effects those around us. Again I use theft. Sure it feels good to have stuff but we have taken from another. As far as drugs go, what you do in your house is your business. Micheal Jackson is emerging as (not that we didn't already suspect) a drug addict (and some serious shit too) but I never once heard about an incident. On the other hand Britney, or Lindsey Lohan or Paris Hilton (one of them dumb broads) has been seen driving the wrong way on the freeway.
I obviously can't deny that I take many of my morals from the society I live in. I think that a lot of the rules that you mention specifically were either written by idiots or in another time. I find incest weird and gross (and I'm skeptical that outside of royal families it was ever accepted, simply because biology generally prevents this in animals) but slap on a condom, get on the pill and go to town. It doesn't bother me cus it doesn't effect me. I'm completely sexist and I can't really say that I think we are better off without slavery, it certainly hasn't been a universal truth. Half the reason we have unions and labor laws and shit is that we found out that when "masters" are no longer required to pay for the upkeep of their "slaves" they simply don't.
What is right & wrong is what hurts others. For instance. Stealing hurts the one that is stolen from. It also hurts the person stealing in the sense that this person now has a weaker work ethic because its easier to steal than to earn something fairly. Now lets look at slavery. There are different forms of slavery. The one for that americans seem to only know about is the kind that took place in the 1800s with blacks that were taken for no just reason and made slaves. In the bible though, the slaves were the people that agreed to be slaves so that their family would be taken care of, or they had a debt that they couldnt pay that made them a slave. The ones that had the debts were most likely the ones that had to be disciplined (or beaten) Despite what visual ideas people have of this, it was not the kind of beating that we imagine. It was the type to correct a person who otherwise was rebelious to his master. The Masters would always first try to talk to the slaves (unless they were bad masters that just enjoyed inflicting pain which of course is wrong) If talking to the slaves didnt work, a beating would happen. Slavery was right or "just" because both parties got something out of it. Sure the debt slave didnt want to be a slave, but he owed money that had to be paid off. Its the same thing today...If a criminal does something wrong, he doesnt want to go to jail, because its hurts him, but its not wrong because justice is being served and he has to pay his debt to society.
Another thing that people love to say is not wrong is sex before marriage. Many will say it dosent hurt anyone if its between two consenting adults, but if you are a father, do you want your daughter having lots of one night stands with strange men? It hurts the parents when they do this. There are some parents that have boys and they are ok with the boy having one night stands, but these parents could be equated to a parent that teaches his child to steal and is proud of him when he does.
Then we have homosexuality. This is wrong because it spreads disease and acceptance of it, can cause young children to "experiment" with it just because they might look up to a homosexual because he/she might be witty, or funny in some way and the child wants to be like him. We see this with other celebrities when they do drugs or things like that. The kids want to be like them so they try what their favorite celebrity is doing. Homosexuality is also not good for humanity as a whole. It does not benefit us one single way. It only makes our population dwindle as homosexuals do not produce children, nor can they raise children in a balance way. Children are more likely to be homosexual if they have two homosexual parents.
The bible is a great book to learn whats right and wrong because God knows what would give humans the least suffering. If we all followed Gods rules, there would be no suffering in the world.
Thiest and Athiest are wrong. Theist and Atheist are right. I do know that much.
Theists get most of their direction from the Bible. Atheists get most of their direction from society, what is popular and politically correct, as you said. However, there is some overlap of the two, as you also know. I figure it is all a matter of conscious. I have trouble doing things some people would not think twice about. Maybe I am just paranoid about being put in jail.