It simply takes practice, patience, practice, patience, and more practice and patience. We have a 30-foot long trailer and a 40-foot driveway. The trailer gets parked along-side the garage, and I have no choice but to back across the driveway over my blind side. (I'd never get it around the corner from the other direction) I have a rather sizeable rock at the 'right' corner of the driveway I have to miss when cutting that corner, then jacknife the trailer across the two lanes of the driveway, onto the gravel that parallels it, and down the side of the garage. Backing to the driver's side is, quite frankly, more difficult as it's easier for me to look out the right window than over my left shoulder.
Find an empty parking lot, set out some cones, and practice. Good mirrors and a spotter who will tell you to stop before you hit anything are a bare minimum.
A practice suggestion that may help: Reverse-engineer the backing. In the afore-mentioned parking lot, park, set out the cones, then pull out and around into the 'street.' Pay attention to the track of the tires and where the truck and trailer end up with the rig straight in the road. You need to do the exact opposite to back it back into the spot. I've found it helpful on my white cement driveway to use the witness marks from pulling the trailer out as a guide for backing the trailer in. After the first couple of trips each year, I have a pretty clear path that the trailer tires need to follow to guide me right back in. :) (on asphalt, you could probably use chalk on the tire tread or sprinkle some sand out...)