There are many things to consider prior to meeting with a recruiter and even more once you have that first meeting. From literally hundreds of jobs, places you could live, career/education goals, and training you will endure should be part of the decision-making process compared to your experiences, skill levels, and interests and desires.
But first and foremost, the consideration to serve your country should be something that you feel a strong desire to do a calling to serve if you will - along with receiving paid education, experience, and leadership/teamwork skills that are highly marketable in the civilian world.
About the Army
The United States Army is the main ground-force of the United States. The Army's main function is to protect and defend the United States (and its interests) by way of ground troops, armor (tanks), artillery, attack helicopters, tactical nuclear weapons, etc. The Army is the oldest U.S. Military service, officially established by the Continental Congress on June 14, 1775.
Traditionally, the Army has been trained and organized to deploy large, heavily armored and equipped ground combat forces, while the Marine Corps was primarily used when smaller, lightly armored, ground forces were required to be mobilized quickly. However, those lines have been blurred since 9/11.
Before 9/11 the Army was organized around large, mostly mechanized divisions of approximately 15,000 Soldiers each. It took a lot of time and effort to deploy such large forces and their equipment, making rapid reaction nearly impossible. The Army then began reorganizing their forces into rapidly-deployable Brigade Combat Teams (BCT), each with 3,000-4,000 Soldiers, along with Brigade Support Battalions (BSB) designed to provide combat support to those teams.
By 2007, the Army had reorganized to 42 BCTs and 75 BSBs, and by the year 2013, the Army plans to have 48 BCTs and 83 BSBs. The immediate concerns of smaller, shorter armed conflicts in the foreseeable future determine the size and structure of our military. The need for larger full-scale division sized movements has decreased with today's smaller and more mobile threat.
The Pros and Cons of the Other Military Branches
Regardless of the branch of service you select, be prepared to deploy to foreign lands around the world. If you like the ocean, the Navy should be a consideration. If you like both land and sea, consider the Marine Corps as an option. If you like jumping out of planes, the Army, as well as all branches Special Operations groups, have members who parachute into combat zones.
If you prefer the land - all terrains - and working with large or small groups through complex maneuvers and missions, consider the Army. If you want to fly planes or helicopters, all branches of the service have them - just depends how you want to deploy - off a carrier/assault ship or from forwarding deployed airstrips and bases. But regardless, thank you for considering to serving our country. Good luck with your decision and future career.