Practice, practice, practice........
IMO, backing any trailer is a hard task to teach / explain beyond the very basics. Things like pulling farther ahead than you think you need to and learn to judge the placement / alignment of the TV and Trailer for best backing is about all you can tell someone. The "scoop" comes naturally to most with some trailering experience.
Personally, I watch closely for specifics like where the wheels of the trailer are in relation to the site / driveway. Watching the angle and distance to the desired place I want it to go. Good mirrors help a lot.
Some get it easily, others struggle forever. The biggest key, IMO, is take your time, no matter what the circumstances are DO NOT GET IN A HURRY!