I came across this interview with food writer, Nicole Cotroneo today on the ways and means of travel writing. I think the advice is great for anyone looking to get started with a freelance writing career (regardless of topic). To break in, you need to realize that writing is work and that you have to work your way up.
Don’t be afraid to start small. We all want to see our byline in national magazines, but the only way to get there is to write, write, write for anyone and anything (well, you know — with some discernment). Prove yourself to the editors you’re working for on a local level and they will recommend you to their friends working in the Manhattan skyscrapers.