Are you ready to quit your job and dive into freelancing?
Hold on: First, see if you can find freelance work in your area of expertise on the Internet. This is a good gauge of what the market demands. For starters, check out the hiring trends at Elance, one of the most popular job sites for freelancers.
Some skills, such as the ability to write coherently or do software design for clients of all types, are highly marketable and you should really have no difficulty whatsoever finding a goldmine of work.
On the other hand, if you are only able to do tasks that are not as easily marketable on a freelance basis, you will have much more difficulty finding work for your freelance operation.