Where everyone else gets them from: societal interactions and negotiations. Most of us want to live in a civil society; morality is how people decide to get along over the long haul. That which sustainably promotes stability and civility is encouraged; that which doesn't, is discouraged -- through a combination of promising / providing / threatening / withholding social reciprocity, laws and penal systems, symbols, taboos, etc. All guided by mirror neurons / empathy. Not just empathy for others generally, but for a particular special other -- our future selves. We have the ability to imagine future benefits and so to defer gratification, to suffer and even die in the service of a better life for ourselves and our loved ones.
I think I had quite a good grounding in manners I was a youngster in 1952 playing out in the road (few cars and they were going slow) the older girls would make the games and we would just join in everything -and we also played (illicitly) in a bombed tennis court that had grown wild climbed trees etc. I think post war London suburbs were full of children because of repopulating post war- We ran wild but had our own rules I was taught to always be polite to anyone who knocked at the door and invite them in - to say 'please' thankyou' and 'may I leave the table please?' I was also taught that no matter how rough someone looked we were to be polite.Apart from that we were pretty ferrule and left to look out for ourselves. Sent out to play in the morning and called in at night (adn aways told not to go near the bombsite)
I don't know how really moral my moral is, neither can I discard or deny strong religious and social influences in forming it.
This a subject worthy of tomes, maybe complete libraries, but we try to summarize it in 140 characters. Because of religious and cultural divides, we do not have an absolute moral code, but one is very much needed. Religious people - of some religions more than others - commit murder in the name of their god. Thus religion is not the answer. The empathy alluded to in the link is not an answer either. Empathy is by nature selective.
Friends, family, surrounding culture.
In Haiti, I had different morality specs for each social group.
For instance, rural Haitians don't believe in one person having ownership of anything (communal sharing), don't think of time as we do, don't have monogamy in their culture, think of clothes as optional, etc.
Therefore, stealing, being two hours late, sleeping around, going naked, etc., are expected, and usually ignored.