The most powerful phrase in networking is a very simple one: "Who do you know who....."

It's an open ended question that forces people to think about how they can
help you. The brain searches for an answer to questions that begin with who, what, where, why, which & how.

A simple example:

"Do you know a person who wants to sell their house? This is a closed
question that will probably result in a "no" answer unless some specific information has regarding a seller has come into the hands of the person who has been asked the question.

On the other hand "Who do you know who may be looking at upgrading their property?" This is an open question that makes the person being asked think
about an answer.

Always ask for referrals by using an open "who do you know who...."
approach.