Most schools ask for two or three letters of recommendation. Oftentimes, students ask their teachers, coaches, or advisors. You should ask someone who knows you well, has taught or interacted with you within the last year or two, and who is not related to you.
Once the person you have selected has agreed to write you a letter, provide them with a list of schools that you are applying to, a resume listing your accomplishments and skills (you can draft this using your college portfolio), and a thank-you note.
Approximately one week before the deadline, send those who offered to write you a recommendation letter a gentle reminder email.