Depends on your level. If you're fresh grad, then it probably comes down to luck (i.e. which team is hiring at the time you are applying), whether or not the team manager likes you, and your interview performance.

Switching BO teams as I understand is pretty common, and also comes down to availability of openings and whether or not someone knows you/is willing to back you. So having a good reputation (being team player, hard worker, interesting person etc.) is impt.

Disclaimer: I can't going into the specifics of skillset since I personally don't have BO experience. It's what I've been told from the BO guys that have reached out to me to network. Probably better if someone else answers that