How do I prepare for life as a new 13F FST NCO?

Your main task at ALC will be to pass your surface to surface CFF, which should be pretty easy since you’ll be fresh out of AIT.
As far as your fist life will go, study planning. You and your FSO will come up with all of the fires plans at the company level so make sure you know how to properly use your echloment of fires. Once you get to your unit, become good friends with your company mortors Cheif. He can teach you a lot about the uses and effectiveness of each system.
Other then that, you’ll just have 5 or soldiers soldiers causing you headaches but you know how to deal with that.

That’s an extremely steep learning curve to jump in as an E6 13F but you’re asking the right questions. Learn from your peers and be humble. Catch up on schools immediately JFO at the bare minimum

As a Vietnam 13F NCOIC in the 4th Infantry Division, you should first keep in mind that you are the King of Battle and many lives will depend on your actions. Your first commitment will always be to the infantry. I would get to know your leaders of 11B & also your 13B's they will clue you in to there tactics for calling down fire missions or there ammuntion counts. Doubling down your FO's wether they are inserted or not with the infantry, need to give you updates on there positions on a timely manner, especially if they are moving with the armor as part of your battalion. Another helpful idea that is very effective are to have your FO's can give you there azimuth of the direction they are looking from there OP. Keep in mind that technology can fail in an instance, see if you can find a manual protractor for range and time of flight to keep with your maps encase of an emergency failure of real time data. Last but not least have your OIC figuring ought your ballistic MET updates. If you ever have any other questions I will try and answer them anytime. Best of luck with your chosen career.