This has been and probably will always be a relationship based industry. If you take a look at the most successful contractors in this industry they always have a roster of key clients which keep them working. You can also see it in consolidations when one company buys out another company. The acquirer might get the equipment and personnel but without the key relationships they don't really have squat. You can't have your new corporate salesman all of a sudden call on a 30 year client and say "Hiya buddy let's go play golf!"
Networking is by far and away the best marketing out there and in terms of expenditures vs. revenues it is really cheap.

I think the yellow pages are a thing of the past. I spent $6k a year 3 years in row on a Dex add only to wear out tires and waste time. Every year the add rep would have a lame excuse as to why it didnt work out but the fact is there people did the add every year and they were not willing to put there money where there mouth is. I told them at the renewal time for the 4th year to run the add for free and cut it off after 6 months I would either start paying or let it go, but they were not willing to do that, If it was working obviously I would not let them shut it off (An expansion line seperate from our main number). I have found activly bidding public projects has been my greatest lead generator. Many generals do alot of private work as well as public and it provides a way to be introduced to those private jobs if you provide a quality service in the public sector. And just flat cold calling makeing the phone ring can be productive aswell. Incidently, I spent $30k on 2 F-150's and lettered them up cleanly and profesionally and have generated over $250 in sales off those 2 trucks alone.