thank you both for those cleared up the grey areas. i know the needs of navy is first come but ET MM EM would be my preferenceorder and no matter which one i get i will like it and give 100 percent. But i havent even enlisted yet. I am trying to choose Nuke, EOD or SEAL. but thank you guys for the help. And i didnt look to hard cause i should have found those post.
allow me to clarify some things for you
1) you dont "choose" EOD, (sp, sorry) "swic"(?), or SEAL. You pick a base rate (i.e. sonar-tech) then you go to boot camp as that. At boot camp they ask for volunteers. You dont have to get those ones in writing. NUKE requires it however.
2) as a nuke, you CAN NOT become ANY other rate without some SERIOUS teeth pulling, and certainly NOT in boot camp!
3) As far as rates go... I dont really believe it matters what your preference is, they just pick some random stuff and put you where you are needed

A phrase you will hear a LOT is... "needs of the navy"
4) if you are serious about SEAL... start running and doing pushups/pullups... a LOT of them

. I have a friend who is in AMAZING shape and he failed out of BUDS.
5) pick MM

good luck on your choice, and thank you for choosing navy