The duties and responsibilities encountered as part of a reenactment unit tend to differ somewhat from what the original company officers did in many cases... Try to take the time and effectively learn both.... Each respective unit and umbrella organization has their own take and forte on it. Hopefully your unit commander will take the time to detail what you are to do and how to do it as it may reflect upon the reenactment environment...
Learn the drill... inside and out... and the proper commands thereof... also duties of the NCO's... In the ranks we drill... drill... and drill some more... the responses and movements become reactionary... Take the average guy out of the ranks and tell them to call out the commands... more times than not they aren't able too... or forget what they were... but if someone else does it... poof do it right on cue.... lol... Go to the officers meetings... any respective advance scenario walk-thorough so you also will know what your doing, where and when... If the commander is absent.... or "takes a hit"... you have to be able to quickly step up and continue the action.... knowledge is the key...
Many groups echo and use reenactorism commands and movements.... try to avoid those if possible... set a higher and more authentic example... Learn the correct paperwork that is typically required of NCO's and Officers.... Practicing penmanship of the era can highlight your position....
Lastly don't fall into the reenactorism habits that every officer must have fancy sword, pistols, sashes, gold braids, high top boots, plumes, lots of glitter and brass that we see so many other reenactor officers engorge upon, and strut about like a peacock... Keep it simple... most of the original officers did too....