First off, speaking as a freelance illustrator, I wouldn't be so quick to pigeon-hole yourself before you've even started. Your new profession can cover a multitude of areas. Art, graphic design, illustration... whatever the next project is, it'll help if you can turn your hand to it. You'll get more follow-on work that way.
I'd suggest sorting yourself a website with examples of your work, some business cards and as much presence on social networking sights as possible (but DON'T start spamming people - that'll guarantee you'll get ignored. Worse still, remembered for it).
Oh, and you'll need a whole hill of patience. It may take time for you to pick up enough work that your diary is seemingly full. Hopefully it won't but the slack time between projects can be demoralising. Patience is key at those times.
Best of luck! It's a fantastic line of work. My only regret is that I didn't make the jump sooner.