That is a pretty big question. I will tell you my 2 cents worth. There is quite a lot that is needed for one to be a good NCO. Read the
NCO CREED to understand the general roll of a NCO. I wish more NCOs actually followed the NCO Creed, especially the putting the needs of my soldiers ahead of my own and the earning respect parts.
What it means to be an NCO really depends on what type of job you are in. I am a forward observer. As a FO, I concentrate on calling for fire while my infantry NCO counterpart concentrates on troop leading procedures. Being an NCO in maintenance, commo, medical and other fields differ greatly aswell.
Here are how things work in a normal company of 5 platoons where each platoon is 30-50 soldiers. The Sergeant is a team leader and/or assistant leader. The SGT may have 3 or 4 soldiers to mold, mentor and lead. A Staff Sergeant is mostlikely going to be a squad leader who is in charge of 9 or so soldiers. IN the infantry, there are 2 teams per a squad. The SGT's are the team leaders. With the infantry, I see the squad leaders being strong in leadership. The SSG can decide what standards his squad will follow and how to get a job done that is given to his squad. A Sergeant First Class is normally a platoon sergeant who is in charge of 4 to 5 squads. the SFC will decide how hard to train the platoon and can really influence the daily lives of his/her soldiers. A First Sergeant is incharge of the entire company's training. The 1SG can do almost anything he wants to since only a Sergeant Major can tell him otherwise. A sergeant Major is incharge of training for Battalions, Brigades, divisions and yes, the Army.
Now here is where a NCO is more powerful in the military. In a platoon, the SFC is in charge of training while a 2nd LT leads it. The SFC has had about 14 years +/- of Army experience while the 2LT has had less than 2 years. The SFC is going to know a bit more on how things run in the Army. I saw new 2LT try to override the platoon Sergeant on a subject. the 2nd LT took it to the Company Commander and was shot down. The same goes for a Sergeant Major has many years of experience. I think most have over 20 years in service. The one in We were soldiers had been in WWII and Korea. That is more experience then an entire company put together. From my experience, when a Sergeant Major talks, you listen
I hope I was able to explain everything ok for ya
SGT Doody