I joined the military to help pay for college and to see if I could actually do what people said was so hard to do. I joined the Army infantry, went to Airborne school, and to a Ranger Battalion for a while, all because I heard it was the hardest thing to do. I did almost 4 years, and went to countries that most people dont want to go to and did things most people wouldnt, but looking back, it was the best thing I could have done. I got the rest of my college completely paid for(including books, spending money, tuition, other supplies) and my college GPA went from 2.0 before, to 3.8 after going back.
As everyone that was in service, I feel that my branch was the best, but cant say anything bad about the rest. I feel Marines and Army Infantry are definately the hardest physically and mentally, but with the Navy, Airforce and other Army areas, there are jobs that can help you throught you life.
Only a couple things I would suggest is to have them not do anything except exactly what they want to do. Dont listen to the recruiters as most of them have quotas and are just trying to push you to where they need you. If they want to jump out of planes, or want to be a medic, make sure it is in writing. Dont listen to the crap about "you can only get it when you are already in." A lot of the time you cant, but they have to give it to you if its in your contract.
The last thing I would tell them is if they are injured in any way while they are in, go to the medic and have it recorded. If their knees or back starts to hurt, go to the hospital at least 5 or 6 times, so it is recorded. During the first year after getting out, they can declare these injuries to Veterans Affairs and get compensation for the rest of their lives for it. I did this and get money every month, extra money on top of the college money they gave me, and free Military health care for the rest of my life because I did this. If there are no records, you are most likely out of luck. If you have any more questions, my icq is 152857888.