ROTC/Service Academy/OCS are the only ways you can become and officer in the united states army. If you enlist, you have the option to become an officer through a variety of different ways like Green to Gold or OCS training later on after basic training.
Accepted offer
Easy interview
Application
I applied online. The process took 4 weeks. I interviewed at US Army (Worcester, PA) in May 2008
Interview
Joined as a high school senior on an ROTC contract. They look for scholar athletes.
I applied through a recruiter. The process took 2 weeks. I interviewed at US Army (Portland, OR) in Nov 2009
Interview
The hiring process is through the military recruiter at the local area. This will detail and present options. Completion of the ASVAB test opens up job opportunities.