Make your feelings known early (e.g. "You have called my house 15 times this week and you followed me home last night. I am uncomfortable with this attention.") If you were in a relationship, you can also add (e.g. "I don't want to continue with our relationship.") Most importantly be very direct and state to the stalker (e.g. "Please stop contacting me.")
Be consistent and firm with your message.
Tell a friend, family member or if you are a student, let a faculty member know what is happening.
Get Caller ID on your phone(s). Get unlisted phone numbers, change your email address, get a temporary P.O. Box.
Contact the Police. It is helpful to have records of emails, phone messages or other evidence of the stalking. Keep a detailed written log of these communications and contacts.
You may want to get a restraining order to require the offender to stay away from you. The offender could be punished with a fine or jail time.