Never hand in a paper before reviewing it. Check the instructions and rubric to make sure you have actually completed the tasks your instructors asked you to. Read through the paper to make sure your ideas make sense, you aren't repeating yourself, and you aren't leaving out any important information. Proofread for errors in grammar, spelling, and punctuation. While computer tools such as spellcheck and grammar check can be helpful, they do not catch everything. Its a good idea to print your paper and proofread a hardcopy as well.