World-building: Creating a Caste/Hierarchy System

You may not be as important as you think. Throughout the ages, countries have had systems regarding who is more important than whom. Even in today's society, there are upper, middle, and lower classes. Creating such a system is essential when world-building.

Top

The top of the food chain is usually monopolized by the government. At the highest place is the leader of the nation, such as the pharaohs, tribal chiefs, presidents, and kings.
Depending on the level of religion in your world, priests tend to be next in line, followed by the rest of the government officials.
If you're "world" consists of one group, perhaps just a family or crew, there are few rules to building. However, the more experienced, useful people usually end up on top.

Middle

The people here are skilled in a way that profits them. These are the merchants, artisans, trades-people and whatnot.
It should be noted, that merchants tend to be above artisans. It seems if you don't have to get your hands dirty, that makes you higher up than those that do.
Of course, not all people here are skilled, such as the wealthy of Victorian England. The wealthy more likely than not had an ancestor who made a fortune that lasted for his future generations to sponge off. In other words, "old money".

Bottom

The unskilled, the homeless, those made poor by corrupt governments. The bottom isn't a pretty place to be and there are few countries that offer the chance to rise up from this level with hard work. For the majority of caste systems, where you're born is where you stay.

Outcasts
In some cases, societies have those that are considered outside the caste system. In India, people born into families who do "impure" jobs (i.e. leatherwork, latrine-cleaning, butchering) are known as the "untouchables". They have next to no rights and are shunned.
This group can include exiles, outcasts, and foreigners.