For a new Specialist coming out of basic, what kind of NCO should they seek guidance from to become an effective leader in the future?

I've found that you can learn from all NCOs. My advice:

1) look for newly promoted NCOs with a short time in service. They're hungry, they're fresh, they're motivated, they can get you promoted too.

2) seek out the guidance of senior NCOs. They've been around, they know the Army and have seen it change over time.

3) find the bad NCOs, they'll be easy to spot. Learn what not to do, how not to be.

4) start becoming a leader. Lead soldiers, so why you can to help encourage and motivate them.

Wow, is this the NEW Army. Didn't know you could "choose" you NCO's. LOL You will have to OBSERVE the NCO's to find one that not only "talks the talk" but "walks the walk". Be wary of those that say "do what I say, not as I do!"

If you are unable to "find" this type of NCO, then become one. This will attract others to you and the exchange of information can only be beneficial to all of you. Be the person that you would be proud to serve under and with.

Your a E4 promotable coming out of Basic training?
Either that is a typo or there is more backstory that would be needed to answer your question.
A: you dont really get to choose your NCO's you will be assigned 1st line supervisor , depending on your MOS, the unit make up and mission that may be a E4 team leader, a SSG Section leader, a WO1, 2, 3 department head, or a Federal civilian....
Now of the many leaders you will likley have direct of common contact with you may find one more willing to listen and advise, one that has like morals, ethics, work ethics as you, and appears at least to be successful in the job, unit, Army.

LISTEN .....choose apropret questions, relative to the job with answers you can not find yourself with even the smallest amount of work. If you think you know the answer better,,, Ask for confirmation after explaining the question, what your research found, your source.

It gets old answering questions a subordinate or peer could have easily figured our for them self... But Most leaders will happy help confirm what you already did the leg work on to learn for yourself.