The Best tip I ever heard was to place your hand on the bottom of the steering wheel, now move your hand in the direction you want the trailer to go.

You also have to anticipate the need for your tow vehicle to follow the trailer, this results in having the trailer making sharper (bigger) turns than if you were just pushing it by hand at the hitch point.

I can also add that the tow vehicle makes a big difference in how big your turns need to be, for example: I now drive a full-size E-250 Ford Van (the wheelbase is almost 12 feet long) this results in very slow (weak) reactions when I try to straighten the trailer out, I have to make my opposite turn sooner than I would have to in any other vehicle I have driven. The one trick I've learned with this Van is to not always try to get the Van to follow the trailer but, if the Van is not following the trailer, to stop and pull forward a foot or two and then continue my approach. This worked really well when I rented one of those U-haul-um Concrete Mixers and backed it into the driveway with a ton of wet/sloshing Concrete in it.