When you move on to the body paragraphs, this is where you will compare and contrast in detail. If you wish to discuss the similarities first, here is what you can do:
Discuss the first similarity
Mention the first person / object
Mention the second person / object
You can follow this pattern for other similarities and differences as well.
When you write, make sure that you move on from one point to another in a very nice manner. There must not be any ambiguities or else your readers will lose interest completely. Make sure that you keep the flow intact if you wish to make your professor happy.
Here are some transition words that you can use when you compare:
Here are some transition words that you can use when you contrast:
Your conclusion will look very much like your introductory paragraph because you will summarise your essay in this paragraph.