Hi there - well get 2 years of experience first, many agencies require this. Then while you are doing this, go to delphiforums.com and sign up for a little free account. Next search and start reading the travel nurse and therapists board. You will learn LOTS. Where the good and the bad places are, which agencies are good or not so great, tax and housing information, just anything you could possibly want to know. They are all really friendly there. As to what specialty, well there is a job for everyone. What do YOU want to specialize in? There is a drop down menu at the top of the page where you can go to the recruiting section and see who is offering what jobs where. 

Finally, last year was the first annual travel nurse convention in Las Vegas. It will be in Sept again this year I think ( have to check the dates). Go and enjoy. Good luck.