As someone who's working on getting a contract right now, I can tell you that you need to get together:
Good ASTB scores (you have to qualify for SNA to get a contract, obviously)
SAT scores
birth certificate
a trip to MEPS
cyclopolegic eye exam
PFT score (3 mile run, pullups, crunches)
application (including motivational statement)
recommendations
transcripts
photo (for the board to see how pretty you are)
Someone correct me if I'm forgetting anything.
What do you mean about "responsibilities"? Like, what comes along with the contract? As far as I know, you are just expected to go to PLC. If you like it, good, if not, goodbye. If you choose to take money from the Corps after PLC, you either have to pay it back (probably with tons of interest) or serve an extra year on your service contract.
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Chris Tessone
http://www.polyglut.net/