For the Spanish settlers, they were pretty much not allowed to trade with any other European country but Spain. This is what many European countries did to their colonies in order to increase their profits. As a matter of fact, many "mother countries" exploited their children or "colonies" by practicing an ecomonic policy known as mercantilism. Using this economic policy, colonies provided the colonizing country with the raw materials necessary to create finished goods. The colonizing country would then ship back the finished good to sell to the colonies for profit. In other words, the colonizing country would export more than it would import. This was done to increase its supply of gold and silver and thus increase its wealth.
For the Native Americans, they were forced to work in search of the gold and silver that the Spanish Crown demanded from the explorations of the New World. If the Spanish government could not increase their wealth from having a monopoly on trade with the Spanish colonies, they would increase their wealth by exploiting the Natives for whatever valuables they had left. This forced system of labor was called the encomienda system. Whether the Natives died from the harsh working conditions, European disease, or a combination of both, they were easily replaced with by thousands more Natives who were commanded by the conquistadors to work in the name of Spain.
If Natives were not working as slaves for the Spaniards, they were forced to work as peons, or workers who had to work for a landlord to pay off a debt. The Natives were provided with food or items that they would never be able to pay back, thus making them virtual slaves to the Spanish. This system was more easily justified as technically providing the opportunity to pay off a debt that was self-incurred but in practice only really benefitted the creditor.
As for the Africans, they were imported by the millions after the Friar Bartolome de las Casas suggested that they take the place of Natives in providing the labor the Spanish claim they needed. Reportedly, they not only worked as slaves but also field hands, miners, or servants in the houses of wealthy landowners or as skilled artisans, artists, and mechanics. The experiences for Africans, like other groups, depended on their particular situation. Some Africans were able to purchase their freedom. However, this would be the exception to the rule. Spain colonial society had already established a social hiearchy in the Americas in which only the peninsulares, or Spanish born, were able to obtain top government jobs. These creme de la creme were then followed by the creoles who were the children of Spanish born parents. Next in the hiearchy were the mestizos and mulattoes, or mixes of Spanish blood with Native American blood and African blood, respectively. Lastly, at the bottom rung of the social hiearchy were the pure Native and African people. In the Spanish colonies, these last two groups would literally be the last to enjoy the abundance of the land and the opportunity to make a good living for themselves.