In your concluding paragraph, start specific and end broad. Use the first sentence to reiterate your thesis in some way. Next you could summarize your arguments using different wording. Vary the depth of what you write depending on the length of the essay. For a long essay you could be more specific and flowery, for a short essay, be to the point. Maybe you could add a little something to bolster or reinforce your arguments, but don't bring up material that diverges too radically from what you just wrote. If you do, you run the risk of confusing the reader, or seeming too diffuse in your writing. After this, you could write about the broad implications of what you just wrote about. Finally you could cap it off by quite briefly reiterating your argument and making a general statement or quote that will make your reader think and then you are done.