1. The Traditional Way: Wrap up the subject of your essay with a single sentence, concluding strongly will help gain marks.
2. If you used repetition in your essay, maybe repeat the line once more at the end.
3. Summing up strongly with a good heavy statement makes the nice impression that you were paying attention and worked hard.
4. Use the sentence you used to begin with, depending on what it is, it may make a nice finish.