All able-bodied adult males, who were not Muslim, had to pay a tax called Jizya. It was quite literally a protection tax as non-Muslims were exempt from military service. Payment of the tax was recognition of subjection to the State and its Laws. It also exempted you from the zakat taxes levied on Muslims for charitable purposes. Originally simply a moral obligation the first Sunni Caliph Abu Bakr made it a statutory one and in return guaranteed every man, woman and child had a guaranteed minimum annual income of 10 dirhams. Of course other communities also had charitable taxes they levied upon their own communities and Christians and Jews expected those who could afford it to give at least 10% of their income to be distributed to the poor.
In later times the exemptions were ended and all non-Muslims regardless of age, sex or status had to pay the tax, in person, and on foot to show subjection. The Ottoman Sultans came to regard the non-Muslims as an economic resource to be regularly fleeced like their herds of sheep and goats. The humiliation of non-Muslims was often officially encouraged by rulers and jurists.
At various times and places non-Muslims were required to wear distinctive clothing or badges and forbidden to dress like anyone of wealth, breeding or education. The Taliban are apparently trying to re-introduce this for very few non-Muslims still living in Afghanistan and Pakistan, for their own protection apparently.
Under the Ottomans a further oppression was the devshirme, a forcible levy of Christian youths, the brightest, fittest and best-looking among the population, into the Imperial service, some to serve as Janissary soldiers, some in the Imperial Civil Service, and the least useful as peasant labourers. All these boys were forcibly converted and circumcised. One group who refused at the instigation of their priest were executed on the spot. Any parent refusing to surrender a son was hanged from his own door sill. Similarly any girl famed for her beauty was likely to be seized and presented by the local ruler to the Sultan as a gift.
Although some of those who prospered in their new lives were able to assist their families the system in part accounts for the intense antagonism towards Islam in the Balkans today.