the first and easiest thing to do is to ask your happy clients for referals, you have a much better chance of making contact with a potential new client from a referal than a cold call. when you hand your client their sign and they hand you the 50% they owe you (because you are getting a deposit correct?
and they say "thank you for doing such a great job" you reply "thank you for your business who do you know that would benefit from my products and services" or something to that effect...and guess what they will give you referals... you may even want to go as far as asking them to make an introduction or at the very least send the potential referal (which is now a potential client) an introduction email or make a phone call on your behalf so that you are not going in cold. if you do this with all of your clients you will build a strong customer base that is constantly generating new referals, any business that has not implemented a referal program really needs to they are losing easy sales.
get involved with your community...get involved with the COC..get involved with networking groups...get involved the business is not going to come to you if you are not actively letting people know you are there and what you do.
take a minute and think about the clients that you have today. who are your most profitable clients? who are the clients that you enjoy doing work for? when you identify the people that you want to work for/with go out there and target those people and businesses. i would much rather take this approach than cold calling to any and every business but if you have no other plan get out there and knock on doors.
make certain that you have an updated portfolio, make sure you are making samples of the work you want to do. make sure you have sample materials with you. make sure you can take an order on the spot if someone is prepared to make a purchase.
after each and every sale make sure you send out a thank you card. ask your current clients what else you can help them with. offer them complimentary products (if there logo is on it you should have a resource, a working relationship, a wholeseller, whatever..so that you can sell those items to them, business cards, letterhead, other corporate collateral, pens, shirts, hats, the list goes on)...and make sure you ask for those referals..i can not say it enough...referals referals referals they are the surest fastest and most painless (imo) way of building a business.