Too often, people are frightened of asking for referrals. Is it the fear of rejection, or are they concerned about annoying their prized clients? If you're providing truly exemplary service, you shouldn't be ashamed to ask for the opportunity to provide that same service to other people your clients know! In fact, it should be the next natural step after asking a client how the service was.
The way you ask this question, however, is very important. Open-ended questions help people to brainstorm, instead of giving them the chance for a simple "Yes" or "No" answer. Instead of asking, "Do you know anyone else who could use my services?" ask, "Who do you know who could use my services?" The difference in how they respond is amazing!
It's also critical to expect the referral. When your tone or facial expressions show that you don't really believe your client will have a good answer, they won't have one! Don't let your body language change your question into, "I don't suppose you have any referrals for me, do you?" Instead, expect the referral like it's the most natural thing in the world. With enough practice, it will be!
If people seem tentative, or they say they'll think about it, tell them you'll get back to them, and set a specific time to do so. Keep the appointment, even if it's just a phone call. Remind them that this is the way your business model works. You "get buys" with a little help from your friends.
You can also use this language in the signature of your email, below your name and contact information. Every email becomes a mini-billboard, even when you're out of the office and have your auto-responder set.
One of the best referral generators I've heard of is simply a delicious fruit basket. Greg Frost, one of the nation's top loan originators, pioneered this technique. He sends a fruit basket to his client after the close of a successful loan. Unlike candy, which tends to get hoarded by the recipient, fruit has a built-in expiration date, so people keep it on display to share. He sends this fruit basket to his client's place of employment, which makes them feel special. When co-workers ask where it came from, the client simply says, "My loan officer gave it to me." This opens the door to many subsequent referrals.