When rewiring and using existing box locactions, what do you do with the wire that is not in use anymore? I usually rip out what I can see. However most is buried and cannot be ripped out so what is an exceptable way to handle this situation?

A handfull of wire-nuts, If I'm feeling cheap, a wad of tape, but wire-nuts are quicker....

I cut off what I can short enough that there would be no way for anyone to connect to the obsolete wiring again.

My opinion is to box off the old wire, tape or wire nut inside of the box might also be good. This way if someone ever does energize that old wire, it doesn't a hazard in the wall. I have seen where an old wire, somhow got energized and was sitting inside a wall for many years before it started a fire.

It all depends, if its an existing cable that runs into an attic or basement or whatever that COULD be used in the future for some unforseen thing, then I will leave the conductors in the box and cap both ends, that is providing its NOT obsolete wiring such as K&T or romex with NO ground.... If its a useless cable ( goes nowhere, has no ground etc.) then I will cut it off short so it cant be used.