When you are not aligned and you don't see a gap between your car and the thing next to you, that is the signal that you need to turn more in order to get where you want to be.

Regarding how far back to go, I find that it's the same problem as parking forward. You just need to figure out how to judge some reference point on your car with whatever is around you. I agree that's one of the trickier things to figure out.

Yeah, the problem with turning is that you don't exactly turn in place, and if you're too far backward, you'll back into the thing you're trying to turn next to..

Forward parking sure has the same issue but for me at least it's much easier to assess depth right in front of me than 2-3 meters behind, through a little mirror. And I mean I can park in front of a wall and leave a 15-20 cm gap between the bumper and wall without much trouble, but it is seriously difficult for me to say whether there's half a meter or one and a half between my rear and the next object. I guess they invented reverse cameras for a reason, I just haven't bought one.

I think depth perception for the rear of the vehicle is mostly a matter of practice. If you can develop spatial awareness of what is in front of you, developing it for what is behind you is just a matter of trial and error.

Yes I meant gap. Just typing too quick and not reading closely enough.