Make time to spend time with your clients at the right time! When you do this you will be able to talk about your work with them, your business and approach the subject of referrals both ways.
We’d suggest getting them out of the office environment. You will need proper time together to do it properly and explain what you are looking for – see rule # 10, yet to come!
Do it face to face, not over e-mail or on the phone. Asking for referrals over Linked-in is very common these days but not nearly as effective as face to face, perhaps over lunch, with a real person, in real time.
Good practice, we feel, is to do it about a third of the way into a project or a few months into a relationship, whenever you feel there is good rapport and trust between you.