Specializing??

Hey... i just had a few general questions about how a nurse goes about specializing.. I'm going to graduate from my program at a Comm. College and take the exam for licensure as an R.N. but after that how do i go about specializing. I'm interested in travel nursing for my first few years and a requirement is one-two years in your specialty. I am currently interested in L&D but not totally convinced... anyways how do you go about specializing? Thanks for any help or advice... oh and btw. what types of specialties have the most travel opportunities?