Kelly Starrett suggests an interesting bracing sequence for core stability in his book “Becoming a Supple Leopard”.
1) stand up straight and squeeze your glutes together: leave your pelvis neutral:
2) pull your ribcage down ( a bit). “balance your ribcage over your pelvis”
3) Tight belly ( I think he tries to please the old Suck your tummy brigade here) I say, brace your abs “A la” Stuart McGill. “Push Out”.(I’ll do a specific blog post on this) I think Kelly also mentions Intra abdominal pressure. This I think is an old fashioned blind alley idea : However his core ( excuse the pun) idea is correct: “tighten up your tummy”. He also, correctly talks about being able to breath with a tightened core.
4) set your head in neutral, shoulders down, I’d add the McGill “anti shrug” here to engage the lats. Long arms. Thumbs forward.