I had consulted to the firm. The CFO called me, and invited me to come in to talk to the managing partner. I knew that they wanted to hire me, and knew that I was a technical guy interviewing with lawyers who were very sharp but not necessarily technical.
I listened carefully to his questions and answered precisely.
He told me he wanted to implement a new computer system - all new PCs, servers, etc. but needed someone to do it. I asked for an 8 day consulting engagement to review his environment and present a proposal.
I completed my proposal, and shared it with him. It was 1/3 less than another consulting firm. He showed me their proposal. I explained where mine differed, and explained that while the other proposal was good there was, in my opinion, a lot of stuff that they didn't need.
He hired me.