Prior service to ROTC (and its subsequent commission). Any tips?

ROTC uses the Ranger Handbook as it’s “training Bible”. Being a former infantryman you have a leg up in that regard. I don’t suspect the coursework will be an issue for you.
I was enlisted for a little over 8 years before I commissioned via ROTC. The thing I’ve see trip up prior enlisted cadets are the inability to get out of their enlisted mindset/checking their ego at the door.

Remember that the moment you become a Cadet you are just that.....a Cadet. You are no better or worse than the other Cadets. All cadets, whether prior service or not, are not your subordinates. They are you peers. They will look to you for guidance as a prior service soldier unless you give them a reason not to.

I hope you pursue and successfully complete ROTC. I look forward to welcoming you to the Officer Corps.

I did not commission that way, but I know most of the rules. First, as prior service with an MOS, you are exempt from the first two years of ROTC. That means you can join in your Junior year, attend Advance Camp, and commission at the end of your Senior year. I've had senior ROTC people tell me that you should do all four years since the cadre will get to know you better, but all the prior service guys that
I know that joined in for their Junior year all finished at the top of their classes and got their Active Duty assignments. I'll let you be the judge on which you think is best.

BTW, if you didn't know this already, Active Duty slots are competitive and how many they have for each class is Needs of the Army. If you plan on going Active, you will need to bust some butt and finish with a high class ranking.

One other thing to think about is the Simultaneous Membership Program. You can re-enlist in the Guard or Reserve, apply of ROTC and join as an SMP. You get the experience since they should be letting you shadow or function as an officer, you get paid as an E-5 to drill, and the time counts toward TIS and to a degree, Retirement. I personally recommend the Guard, since most states have tuition assistance or some extra educational benefits. Your membership does not effect your ability to go active as long as you don't take a GRFD scholarship.

I already had a 4 year degree when I enlisted, so back then that limited my options. I can tell you that I would chose the ROTC route in your shoes, OCS is a royal pain in the ass and I disliked all my TAC's.

I am a prior service officer who commissioned from ROTC. As mentioned below, check with the desired college about ROTC availability and likelihood of admission. There are many former NCOs who become officers from ROTC, but there are requirements that need to be met (e.g. age, medical status, academics, PT testing, etc.)

https://www.goarmy.com/rotc.html

Best guess would be to check with the ROTC commander or admissions to see what you have to do brother SPC (Join to see)

One final thing I forgot to mention. Academics needs to be your main priority while during ROTC at college. It doesn’t matter how fast you run or how well you can conduct battle drill 1A if you can’t successfully graduate on time. No degree = No LT.

I am currently an SMSI in ROTC. Regardless of background G2G (Green to Gold), prior service and ANG/RC Soldiers bring a wealth of experience and knowledge to the program. Your insight with your peers will be immeasurable if you educate them. Being selfish or not a team player in mundane tasks will get you nowhere. Look at every opportunity to share knowledge and experiences with your cohort. Think of your crawl, walk, run model as classroom, labs and FTX/CST as far as training progression goes. Be prepared for cadre to rely on your experiences and put you in leadership positions expecting you to do what is needed to be done and provide direction, purpose and motivation. I have had several prior service or guard infantryman and none of them commissioned infantry, not because they did want it but because they sucked. Be humble and take everything with a grain of salt as things in doctrine have probably changed some since you have been in, like the ACFT no longer APFT. I think ROTC is the best commissioning model because you learn some basic knowledge before BOLC and because it helps transform you as a leader while also still getting to experience life as a student. Good luck! Come to Iowa if you want to be the best. Go Hawks!

If you are completely out and out....your only options are to get back in and apply for OCS, or go to college and go thru ROTC...or if you already have a 4 year degree then see if you can direct commission. That's pretty much the options.

Did you end up in ROTC?

I went AD E-1 to E-4, got out, did Guard PLDC then directly to ABN as an SMP Cadet. I went to Advanced Camp at 23yo & like some of the posts here, I had a difficult time w the Cadet culture which was effectively "cheerleading" (or in the day called "Spotlight Rangers"). You will be evaluated as one Officer posted on Light Infantry tactics, precisely the Ranger Handbook. In "my day" there was a peer evaluation matrix in play so getting along w the culture and squad/platoon because the numbers of "A+", "A", "B+" ratings (4's systems) were competitive & limited. Check ur ego at the door. Put the edge on the blade of your small team leader skills and go for it! Best of Luck! So many of us would do it all over again, our careers were just so satisfying!!!

Be humble and always remember you have two ears and one mouth, listen as twice as much as you talk. You will have seniors over you that the closest they have gotten to active duty was a wet dream after watching Full Metal Jacket. When I started my first semester as an MS1, I had done CAP, JROTC, drilled for almost two years, and just finished AIT before going on contract. I was 18 and full of ego I did not earn although I thought I did. I needed to shut up and listen, something that took many more years.