1) Make sure you're using the correct email address: many people have multiple email addresses, and try to reset their password using the wrong address (e.g. their Gmail account instead of their .edu account).
2) Be patient! Password reset emails may take a few minutes to appear in your inbox. Please note that every time you request a new password reset email, it invalidates all previous password reset emails that you have been sent as a security precaution. This means that only the most recent password you have been sent will work.