Experienced nurse trying to get into ICU/CCU/ER

I have been an RN since 2002 and have primarily worked med-surg and LTC. I am applying to ANP program for the fall/spring of 2010. I would like to gain some experience in ICU/CCU/ER. Any advice on the best ways to go about this. Should I start by becoming ACLS certified? Thoughts Suggestions or any one who has experienced this to give some advice would be greatly appreciated.