What would I need to really focus on or study if I decided to transition to an 18 series MOS from a noncombat/support MOS?

Rucking, lot's of rucking, running (a five mile run should be easy), land navigation, SUT, and the Ranger Handbook (your bible if you make it past SFAS). Don't think about it too hard, just go, and if you go, DON'T QUIT. The rest you will learn in the SFQC, on the job, or in the many advanced schools you will have the opportunity to attend. One more thing, if you make it onto the teams, ask for Ranger School ASAP. It will greatly benefit your career track, open doors that "don't exist", and the sooner you go after the SFQC the easier it will be.

SGT don't worry about being a badass, just don't quit and pay attention to your body. I will go ahead and tell you will hurt, you will hurt worse than you have ever hurt before. Just know it is not fun, take it one day at a time, one event at a time, one step at a time. I think it is a great decision and I wish the best of luck.

Everyone will say PT and rucking, but since you are asking the question and I assume have done at least a bit of homework, I'll go another way.
Think of yourself as a member of a team that must be reliable 100% of the time. Think like you are always the one navigating, thinking ahead, looking for a defensive position, responsible for evac... because an SF team member must be interchangeable with every other member. If you aren't, you are a liability. It is more than just pulling your weight. It is the distinct possibility that you will have to carry your weight, carry your teammate, and still accomplish a mission with little or no guidance.
It is a mindset that is hard to get into, especially if you spent any length of time conventional and become conditioned to expect others to cover their ground while you cover yours.

My former squad leader (SSG, 11B) worked his ass off to get into SF. He spent his private time learning all he could learn, and PT, PT, PT! This guy not only did morning PT with us, he PTed on his own and in the afternoon was in change of remedial PT.

He got through selection, training and eventually made it.

He was killed on his first deployment as an 18 series.

As far as Selection goes, those that I have talked to that wear the Tab, they all agree on that you need to work on PT prior to arriving. There was this CPT at Lewis that once told one of my Soldiers to start rucking now. Work on your endurance. Land Navigation, as I understand, is a section that kicks a lot of Candidates asses. Lots and lots of Team Building exercises. Here is a link to a documentary on SF Candidates. It may not give you all the answers, but it should give you an idea as to what to prep on.v Good luck

https://www.youtube.com/watch?v=wldw-ZCS9j4

Get in the best shape of your life
Ruck ruck ruck
Get your feet tough as nails
Do PT in the AM then as soon as you are done ruck a while. Ruck while carrying stuff, take care of your feet

Carry a big heavy ruck as often and as far as you can.

It depends on what you want to do, Medical is the most
extensive and long but if you wanted to leave service, you could find a good job or become a nurse practioner or a PA Warrant in uniform. Commo you learn a lot about electronic goodies, while intel can lead to futther service in some of the alphabet agencies.

PT is top of the list. Endurance and know how to climb ropes it's a skill. Climb ropes 3 times up and down for a few weeks before selection. Land nav with ruck and up to 50 pounds minus water. 12 mile rucks. After selection find an infantry buddy that is Ranger qualified and learn patrolling. If possible ask SF recruiter if you can do 18X program. Soft skill mos's is difficult, but not impossible. Only issue if you go to Ranger school before SF is you owe your unit 12 months after. The SF recruiters have a good book for preparing for SFAS, if your doing PT, swimming, rucking and weight training you can get thru. Good luck and look at the SORB website for answers.

Mentally they will teach you everything that you will need to become selected and make it through the course. The one thing they can not do is get you prepared physically you need to do that on your own. The whole course is like drinking information out of a fire hose and then how well can you perform the tasks that were taught to you. I was support before and have tons of team mates that were as well but it all comes down to how badly you want it... and a little luck

I honestly don’t think there is anything you can study that will help with selection. My advice would be to ensure you are as healthy, mentally and physically as possible going in. This as well as being used to carrying a 45lb plus water ruck for varying distances over varying terrain will help you be as prepared as possible.

The physical portion is always brought up, and yes it is demanding but it is partially just a means to break you down and see how you react to stressors. What do you do when you are put in difficult situations while sleep deprived, hungry and worn down.

To me it’s more of a mental assessment than a physical. Again the physical is to get you to a point where your mentality can be assessed. This is why I say to be as healthy mentally as possible going in. You don’t need to be worrying about things at home or outside stressors detracting from your focus.

The most important thing is to make it through the selection course. If you can make through that, you can make it through the rest of the training.

So, did you go to selection?

Never quit. Don't over train, stay away from supplements. Do your homework, make sure you can afford the time away for training and deployments. Never quit.

Land Nav, Land Nav and more land nav...biggest washout group on SFAS on my rotation was land nav....PT is a given, and with your current MOS, should afford you the time, nutrition and facilities to get in your best condition. Above all, no matter what, DONT QUIT!!!!

For selection, I would say running and rucking.
I am a small guy. I weight about 155 pounds going through, but was a runner and could ruck really well.
You will need the endurance. Guys my size, I believe, also tend to fair better as long as you can carry the weight there without getting hurt.
Others will have other opinions, but that is my advice.
Also, go with the ability to at least max the APFT, if not far exceed.
Otherwise, don't let the mindgame get to you. Most of the guys that were dropped or quit, it was because they let shit get to their heads. "I'm not gonna get selected." "I didn't perform well enough" "This sucks" etc etc. Just get through it. The first step is simply getting through.

Everybody says PT and rucking. While this is true you need to know land nav. This is a for sure way to get sent home if failed. DO NOT QUIT!!! Do your very best!! One task at a time.

Do you know any other languages?

I'm currently going 18X from an 11B although I'm a reservist so I'm also working on transitioning from the Reserves to active.