If your work is good and your rates relate then generally people will snap your hand off. Seems to me there are a lot of charlatans about these days so once you have a couple of happy customers the work show flow - Word of mouth is by far the best promotion (and relegation) tool.
A decent portfolio for client review, listings on the creative jobsites and some good old fashioned phone calls will get you moving too.
Then volunteer your time to a charity. Many charities are in need of site redesigns and even if they do not have money to give you they do have Tax id numbers and can give you a reciept for services that you can use as a charitable donation on your taxes.
Use the charitable sites to build your portfolio, develop word of mouth in your community, and hone your skills working with a client.
You said that you currently work as a designer. One thing to watch out for is conflict of interest with your employer. If they sell graphic design and you are selling graphic design on the side then it will lead to trouble. Tell your direct manager or the HR department at your full-time what you have in mind to do. If you do not think that they would take it very well then there is a good chance that you have a conflict of interest.
Developing sites for charities is a good way to get experience, and it's generally a nice thing to do anyway, but you can't deduct the value of your donated time on your taxes. At least, not in the US you can't. I'm guessing this link will be allowed here: [ustreas.gov...]