Like others have said, a website is a must. Doesn't need to be anything special, just clean with numbers and basic company info. Show some different job sites and start getting in with other contractors. Sometimes doing the cheap job for a "friend" turns into something much bigger. Advertise at ball parks and mingle with people.
Everyone is out there trying to help out their buddies now, so the more buddies you have, the more they will help out and throw your name around.
Try to find something that you like doing within your business (cheap, quick, and useful to many) and advertise deals for it wherever your are putting fliers and what not. Make sure it is on your website. People use google, yahoo, and the like for everything now. If they google excavating company (for example) and that's what you do, you better have something for them to look at.
I know it is not always the case but nowadays people regard businesses without websites unprofessional many times.
Website, Website, Website
This is another huge one, put a decal with a number on your vehicles/trailers/machines. Drive that vehicle everywhere, when your going to eat, when you go to a movie, when you go shopping, and when you go grab your 12-pack. Make a couple shirts or a hat that you can wear around and people will begin to notice.
You are right on that business comes mainly from word of mouth and that sort, however, that could take some time to get the initial business customers so these are all things that will spur you along. They are rather cheap and promote a lot of good vibes from your company.