That's all there is to it. You should never mail out or hand over a resume that isn't perfect. Have someone help you edit it before you let an employer see it. Using active verbs instead of passive verbs is better on your resume.
Big paragraphs are too much to read on a resume.
Try to use bullet points and give the reader clear examples of your accomplishments, instead of writing a long description of your daily duties. If something changes on your resume, revise it on a computer. If you're still in high school, it's OK to list your high school and expected date of graduation on your resume. You don't have to give your GPA or anything like that, but if you've done something really special in school, like won a big award, you can add it.