Slavery in Uruk
Generally speaking, slavery in Shem and Uruk follow the customs of what we would consider "Biblical Slavery" - that term alone is vague, but it is important to note that slavery in the world of Conan was not similar, or equitable to Gorean moralities. This is not a wholly patriarchal society, men and women were enslaved equally, and there was no special emphasis upon sexual slavery. There are no customary methods of walking, talking, kneeling, etc, but rather a series of laws which dictate what can, and cannot, be done to a slave.
There are many ways in which one can become a slave. Some are born into it in the case of parents being slaves. Others are enslaved as captives of war. As a rule, it is severely frowned upon to enslave any man or woman merely on a whim. Particularly in Shem and Uruk, slavery was not forced upon anyone unless it was a punishment for a crime. Enslaving someone whom your character merely dislikes could result in heavy consequences for your character, especially if they are native to Uruk.
That being said, there is a profit in slavery. An enterprising seedy character could quite easily club someone over the head, and sell them to a slaver to make a quick bit of coin. In that instance, a person must rely upon friends and family to produce evidence that they are not truly slaves. Those without familial backing could easily find themselves in a bit of trouble.
It was also possible to be born into slavery. If a male slave had been given a wife by his owner, then the wife and any children which had resulted from the union would remain the property of his former owner.
Occasionally debts happen. When loans come due, or business transactions fail, it is not uncommon to pay off one's debt by willingly enslaving yourself to the person whom you owe. Others choose to enter the arena, in the hopes of winning enough to pay the debts. This could also be described as indentured servitude. Often this lasts for a set period of years, or when a debt is managed to be paid.
Debt slaves were one of the two categories of slaves in Uruk's society. As the name implies, these individuals sold themselves into slavery in order to pay off debts they may have accrued. These individuals were not permanently in this situation and were usually released after six to seven years at most. Children of a deceased debtor may be forced into slavery to pay off outstanding debts. Similarly, debtors could be forced to sell their children into slavery to pay the creditors.
This ties into the justice system of the city. Punishment for various crimes often results in a fine. Corrupt guards who are working for a bribe, may increase the fine. Those unable to pay, would end up enslaved until the debt, and bribe, is paid.
This is the most common form of slavery found in Uruk.
Chattel or Prisoners of War
Chattel slaves, on the other hand, were less common and were usually prisoners of war who retained no individual right of redemption. These chattel slaves engaged in full-time menial labor, often in a domestic capacity. In Uruk, captives obtained through warfare were often compelled to become slaves. If the soldier desired to marry a captured foreigner, there were stipulations. She or he would shave her head and wear no jewelry or cosmetics to mourn the friends and family whom were killed in the war. While the term may be different depending on how many were lost, it would be for a minimum of one month. After the grieving was over, then he or she was free to make wedding plans. If the soldier wished to end the relationship, the code stipulated he must free the slave. Because soldier forced her by the point of the sword or tip of the spear into a sexual relationship, they forfeited the option to sell the captive into slavery. Those who had been sold into slavery were regarded as a type of property that could be inherited. Foreign residents were included in this permission, and were allowed to own slaves.
Like debt slavery, occasionally a man or woman is placed in a form of sexual slavery. More commonly, they are owned by brothels or taverns, rather than individuals. However, as it is a religious custom to use temple prostitutes, and sexual activity was considered a form of prayer, the most common use of sexual slavery is quite literally, to breed more slaves.
While this exists in Uruk, it is less common that indentured slavery. Even prisoners of war have a hope of someday gaining manumission, if they work hard and distinguish themselves.