Understand what kind of lead this is
A directory enquiry is a shared, low context, time critical lead. The person has a need, has expressed it in a few words, and is very likely to hear from several of your competitors within minutes. They know almost nothing about you, they have not read your website, and their impression of your business will be formed almost entirely by how the first conversation goes.
Every practical recommendation follows from that description. Speed matters more than polish. The opening thirty seconds matter more than the brochure. And qualification has to be fast, because the person is fielding calls and is not going to work through a discovery framework with a stranger.