I second ELS, goinggreen123, and cpllawncare. They gave some great advice.
You also hit the nail on the head.... After word of mouth; trucks, trailers and uniforms are the best advertising you will ever have. Make them as clean as you can with a nice logo.
You should also type a professional letter/resume that details your experience. You have good experience with great clients, make sure to point that out. List some of the best customers you have worked for. Ask for referrals from some of the property owners/managers you had a relationship with. Spend some money to have this professionally written if you need to. You can also use this information on your website or a flier.