Thank you! Yeah getting as much experience as you can is the best thing you can do. Anything involving animals is helpful, and the more experience the better.
There are many marine parks across the country that offer training internships. Here is the website for the SeaLife Center in Seward, Alaska if you want an example. http://www.alaskasealife.org/New/about-ASLC/index.php?page=internship-program.php.
There is also the Exotic Animal Training and Management program at Moorpark College. They have a teaching zoo and you pretty much run the zoo and take animal behavior classes and whatnot for two years. I know that many marine mammal trainers have done this program.
Also, here are some books that I found quite helpful:
http://www.amazon.com/Kicked-Bitten-Scratched-Lessons-Trainers/dp/B000NNX1XC - this one describes what EATM is like and what it takes to be in it.
http://www.amazon.com/Starting-Career-Marine-Mammal-Trainer/dp/0971985324 - this one gives an overview of the things you need to do to become a trainer and it also has a list of all the marine parks in the US that offers internships.
http://www.amazon.com/Dont-Shoot-Dog-Teaching-Training/dp/0553380397 - This book is excellent if you want to learn the basic principles of clicker training and how it works (which is what most if not all marine mammal trainers use only with whistles)
http://www.amazon.com/Lads-Before-Wind-Dolphin-Trainer/dp/1890948047 - this one is about a dolphin trainer/researcher and her experiences training.
http://www.amazon.com/The-Dolphin-Whale-Career-Guide/dp/0966067568 - this one lists and has a 1-2 page description of all the marine parks and research facilities in the US
SeaWorld also offers career camps where you learn about each of the animal careers by talking to and assisting the trainers and keepers. SeaWorld San Antonio offers a college camp, which is pretty much the same as the advanced career camp. It is kind of expensive, but it is truly an amazing experience and if you get the opportunity, I would highly recommend you go. Here is a link to the website: http://seaworldparks.com/en/seaworld-sanantonio/educational-programs/resident-camps/marine-zoological-careers/
Some other helpful websites:
http://www.imata.org/index.php/become_a_trainer?cfid=35 - IMATA is great association in general for anyone who is aspiring to be a trainer. You can read more of what it’s about and stuff on the website as well.
#marine mammal training
Anyway, there is all kinds of stuff out there. You can google marine mammal training and find all sorts of information. These are just the things that I’ve personally found most helpful. I hope this helps you some, and if you have any other questions don’t be afraid to ask! :)