What I was told when i first started with horse trailers was
when going forward, to wait until it seemed almost too late, and then turn hard.
Backing up, turn a little bit seemingly almost too early, and then watch for the trailer to react, and then follow it.
School parking lots on Sundays, maybe a large manufacturing facility, and use the lines to learn your rigs characteristics.
Campsites generally are less than 20 feet wide and that is using some of your sitting area.
Think about the ones you frequent, likely they only have about 4 feet extra on the drivers side and no more than 10 or so on the passenger side.