Just found another YouTube video about backing in. It is short,funny and has a good tip.
https://www.youtube.com/watch?v=RLtfrBWzNCw
One thing I learned awhile back is to put your hand at the bottom of your steering wheel when backing up. That way you don't have to think "opposite". If you want the trailer to go right, you move your hand/wheel right, etc. Works good for me.