be sure to have your physical training under control (start working out if you havent already) swimming, threading water, push ups, bent knee sit ups, running (1.5miles), be sure to know the ethos, the eleven general orders, phonetic alphabet, the slang terms,. all this can be found in The Helmsman (
http://www.uscg.mil/hq/capemay/docs/pdf docs/Helmsmannew.pdf)
good luck!