This is a tough one. I can tell you one of the ways I researched.
I looked up various schools to see their admission criteria. It helped me focus of what I need to do to apply.
I understand that most students do not have their "mind made up" with respect to the carrier options, but just want them to know that being proactive helps!
For Defense, this outlines everything:
http://www.nda.nic.in/html/nda-admission-details.html
It all depends on their interest. We can help them channelize this interest if seeked.
Prashant, it would be a good idea at this to talk to them and find out broadly what they know and don't know. Kids these days are really smart and we should help them achieve what they want in the easiest manner possible for them.