This National Guard Manual by Pinckney is a fantastic resource to understand many specific details about military life, duties, and equipment.  This is a must read!  Don't take my word for it check it out yourself.

CLICK HERE

Google books has a fantastic selection of Civil War publications free.  Sometimes it can take some creative searching, though.  Taking a look at period manuals is a good way to get a sense of what would have been expected of our duties.  Here is a link to a good book for company officers:

Hints to Company Officers on Their Duties by Capt. C.C. Andrews of the 3rd Minnesota Regt.

Such topics include:

• Business capacity and Responsibility
  
• Military Responsibility
  
• Character
  
• Morale of Troops
  
• Treatment of the Men
  
• Fortitude
  
• Valor
  
• Superiority of Valor and Skill over Number
  

Feel free to post a comment if you have other sources to recommend.

Duties of the 1st Sgt.