Well first you get the money, then you get the power....then....ooooh no wait wrong advice. That's for cuban gun totting drug barons, I'm sure you aren't one of those :icon_biggrin:
Well you need to figure out your target audience, then figure out who your competition is. Choose your battles. There's no point in competing with the big agencies, at least not when you are starting out. So think small to start with. It might be through friends and family at first, somebody might know somebody etc etc. And it would be better to focus on your local area, again this cuts down competition more. Then its a case of making yourself known to businesses who may want your Graphic Design. One good source is to go through the phone book of your target audience. I was told one good way to introduce yourself is via letter. It has to be extremely well presented, signed and in a hand addressed envelope. This gives is a more personal touch, and is less likely to be chucked as junk mail. Change your wording to fit the particular business you are aiming at, keep it very brief and include the benefits of hiring you (e.g cheapest in town!) and add a call to action eg. visit my website. Give it a week then follow it up with a phone call "Hi, I'm a professional freelancer, I have been introducing myself to local companies. Oh you got my letter, great....etc etc."
You get the idea. A lot of it is marketing yourself and making yourself known to people. And don't lose sight of the fact that what you provide should always be for the improvement of profit for your target business. If your target business don't see your service as profitable or advantageous to them, they won't hire you. Give them a reason to spend money on you.
Who knows, if your boss goes along with it you might even convince him to send you on a Marketing Training course!