Ask specifically rather than generally. Naming the client type wanted, such as another contractor frustrated with job costing, produces far more referrals than asking whether anyone comes to mind. Once a year with each client is enough.
The difference between a firm that gets referrals and one that does not is almost entirely the specificity of the ask.
"If you know anyone who needs an accountant, keep us in mind" produces agreement and nothing else. It asks the client to search their memory against a category, which is cognitively hard and easy to defer.
"Do you know another contractor who is frustrated with their books?" produces names, because it describes a specific person in a specific state.
How to run it:
Do the same with professional partners, in writing. A one-page description of your ideal client, including who you are not right for, is what turns an attorney or banker from an occasional source into a reliable one.
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