One of the best tips I ever got for backing a trailer and I shared with my wife was "Put you hand(s) on the bottom of the steering wheel and move your hand in the direction you want the trailer to go.
She went on to drive our Motorhome cross country several times. Of course, if you are towing a car 4 wheels down you can't back up (well maybe 5 or 10 ft. but it will jack knife before you get very far)