what should I expect to do as a S3 NCOIC, how can I prepare?

Have you been to/requested Battle Staff NCO course?
Bottom line: all 3 shops are different and run different based on 3-actual and your OPS SGM. Get with you SGM and get a clear understanding of their expectations of you and go from there.
A good left/right seat transition is ALWAYS helpful as well.

well - first and foremost, you are not the NCOIC of the 3 shop, that would be the OPS SGM, Second, you are going to be responsible for running day to day activities of the Schools NCO, Land and Ammo NCO, the command groups drivers, maintenance schedule of the TOC's equipment, producing the duty rosters and DA 6 for staff duty, and whatever else the 3 actual, and OPS SGM decide. Hard Job, but when you get things going smoothly, it is rewarding.


the actual friction that will occur is the head butting of your 1SG and the OPS SGM when it comes to taskings, as the OPS SGM like to task the HQ company without realizing that the HQ 1SG only controls maybe 30 people. the rest of his company is the S-1, S-2, S-3, S-4, S-6 and they all have captains or above in charge that answer to the BN/BDE Commander, not the company commander.