How do I compare and contrast?

When we are comparing and contrasting, we are looking at similarities and differences in two things. They could be two people, two events, two situations, or two objects, for example.  I see that you have asked this under the heading of "history," so I am assuming you are expected to compare and contrast something in history.  I will give you a few examples and then explain how to organize a compare and contrast essay. 

One kind of useful compare and contrast analysis in history is an examination of how two wars are the same and are different.  For example, as the United States has been looking at the war in Afghanistan, it is helpful to ask how this war is similar to the Vietnam war and how it is different because that can help us decide whether or not we want to continue to engage in this war.  The war in Vietnam was similar to the war in Afghanistan in that we were engaged in a kind of guerrilla warfare, not a traditional kind of war with a "front" to fight on.  A difference is that the war in Afghanistan is over religious extremism, not over communism versus democracy.  There are many other similarities and differences that can be looked at.

Another kind of compare and contrast that can be done is to analyze two leaders, for example, two presidents of the United States or a president of the United States and the president of another country.  Clinton and Obama have similarities and differences.  Both have espoused liberal policies for the country, but Clinton's personality is quite charismatic, while Obama's is more cautious and professorial. 

Two countries can be compared and contrasted, too, for example, the United States and Australia.  Both were developed by many involuntary "pioneers," slaves and convicts. Both seem to have far more coastal development than interior development.  A major difference is geographic, since Australia has far less water than the United States, much of Australia being an almost uninhabitable desert. 

When we write a compare and contrast essay, there are two ways of organizing it, the point by point method and the block method. In the point by point method, we write a series of paragraphs in which we discuss one point at at a time, whether it is a similarity or a difference.  So, if we were writing about the United States and Australia, there could be a paragraph on geography, a paragraph on how the countries were founded, a paragraph on their respective politics, and a paragraph on their natural resources.  In the block method, we would discuss first all the similarities and second all the differences.  Once you know what the objects of comparison and contrast are going to be, you can make a list of similarities and differences and then decide which way you would like to organize your essay.