One of, if not THE biggest, mistake people make when trying to get referrals is that they ask too soon. You need to make sure the following things are in place to make sure your referral marketing will work.
1) Trust from the person you asking a referral from
2) The person must belief that you offer value
3) The person must believe you will not embarrass them
4) What is in it for the person who is giving a referral.
Once these things are answered you should generate referrals in your business.