Classification
If you wanted to show that the assassination of General Trepov by Vera Zasulich was an act of terrorism, the classification method, which usually involves putting a subject in a larger group in order to consider it more closely, would work well. To classify you need to define the larger group (i.e. What is terrorism?) and then show how Vera Zasulich's actions fit within that larger group. Her intent, for example, was not to actually kill Trepov but to use violence to gain attention for her cause through a public trial.
Comparison / contrast essays are a specialized form of classification organization. To compare any two items successfully, the items must belong to the same larger group. When you compare, you still place the items in the context of that larger group. However, you will proceed with an additional step. Once you have established the features both items share with the larger group, you will discuss their differences as well. For example, if you wanted to compare the Rwandan Genocide with the Holocaust, you might note that both resulted in the deaths of a large portion of a particular population, that both were instigated by people in power, and that both were supported to one degree or another by the actions of ordinary people. You would then explore the differences between the two, such as the difference in how ordinary people participated in the genocide or possibly the role of technology in each case.