We get a few each month and find that we convert 100% of web based enquiries.
Ours come in from searches, I was #6 on google before our last revamp and dropped back to 5 pages down but back up to second page and still climbing.
I am revamping our website again for relaunch in new year so that may drop us again.
I pay a small fee to YP online and have it linked stright through to my site and most come in through that way.
I walso have it EVERYWHERE, bus cards, invoices, all adds, thankyous, latterheads, faxes, vehicles etc you get my drift.
Works for us.
John