go to a place like Fast Signs, a vinyl sign company store (normally in strip malls). have them professional letter up your vehicle with pictures, etc, not just some cheesey letters from Lowe's on the tailgate.
Either design yourself or have like Kinko's or a small printing place design some business cards to match. I would even go with uniform shirts. Most uniform company's offer a wide range of items from polo shirts to full decked out items. They can embroider and silk screen the company name on them as well.
key #1 - Image is everything and speaks volumes for you
advertising....local small papers, you can run ad's for pennies in the Trade's section. post a pre-made listing (even in HTML w/ images) into sites like CraigsList.org for your area and any near by towns. post flyers in all the grocery stores on the coupon and announcement boards. same goes for all the gas stations, and mini marts.
look into 5 and 10 second ad's on radio stations. just market it towards your clients age and time they would most likely be listening. look into local coupon papers, books and envelope packages.
offer a coupon, discount or even a rebate for any customer that brings you another customer. so say you charge $100 for the job, if they bring you another customer, you will rebate them $20. word of mouth is one of the best advertisers.
approach condo and apartment complexes. offer to do 1 deck for free to show them the service then sell them on doing all the decks in the community. same can go for some housing communities that have an organization that controls them. sometimes you can find in their by laws that they must keep fences clean or sidewalks clean, etc. great point for you to push, its a "must". (I do this with cars and certified used is my hook, for I do touch up paint work and certified cars have to be "perfect", so you have to use my service).
Don't leave out commerical for many gas stations, restaurants, strip malls, etc all like to have their sidewalks washed, parking lots washed, buildings, etc. When I was a store mgr for McDonalds many yrs ago, I had a company come in once a month at night and power wash all the sidewalks, drive thru lane and all the parking spots next to the building. remove all the gum, spilled coffee, pop, food, etc. same goes for gas stations, etc, they need to clean up spilled oil and messes around the pumps.
PS - don't forget about a basic web site as well. doesn't have to be fancy but just info on what you do, what you offer, about the company, contact information, address, phone numbers, etc.
start simple buy a silk screening kit it will come with everything you need except maybe fabric ink
and and see what issues come up