Becoming a Vice Captain?

[Wadei]

In any of the databooks, did it say how Vice Captains are appointed? From what Aizen said about Hinamori, it seemed as if he appointed her to the position. However, it doesn't particularly seem like Byakuya likes Renji enough to appoint him.

Other VCs seem to have gotten the title out of convenince, like Yachiru and Nemu (not saying they aren't strong, but they have personal connections to the Captains,) so I'm just unclear if they're approved by the 13 Captains as a whole or if each individual Captain appoints who they wish.

[Nowitzki]

The Central Office of 46 can appoint Vice Captains. In instances like Aizen's, he opted to appeal to the Office of 46 so that positions could be put into his favor (Hinamori for him, Kira for Gin). This also how transfers work. The motion is through the Captain, but the majority of the decisions come down to the Central Office of 46.

[Yamamoto]

in one of the profiles, itis said that Yachiru is the only VC that did not have to apply and take the test for the position (kinda like Zaraki and captain)..

[Undying]

You basically need to be strong. Fit to certain standards and you got your desired rank.