It does take some practice...
Assuming you are lined up pretty close, get out and look....in the trucking industry we refer to that as G.O.A.L. Get Out And Look.
Don't be afraid to back up a bit, then Get Out And Look. Then back up a bit more, then GOAL...Get Out And Look.
Do this over and over, moving a few feet or inches at a time, until you are fairly close and make sure everything is lined up horizontally and vertically, adjust the trailer tongue jack as needed, and repeat until the hitch ball is directly under the trailer coupler. Don't be embarrassed to pull forward again, as many times as it takes, and get lined up. If you have no spotter helping you, and no rear-facing camera, and no backing markers as mentioned above, then this is the only way to do it safely.
When you are still several feet away, like between 5 and 10 feet, you can step off the distance from your hitch ball to your coupler, lets say its about 7 feet. Then, pickup two pebbles, rocks, sticks, little blocks of wood, whatever, and place one on the ground even with the front edge of your driver seat cushion, then step off about 7 feet rearwards, and set the other pebble or rock down on the ground at that distance.
Now you have a rough guide on the distance you need to back up to be ready to couple the hitch. Hold your door open and assuming you are lined up, back slowly while watching the markers you have set out. Close the door as needed to use your mirror, then open the door again to spot your markers. Stop when you are about 2 feet from being lined up and then, you guessed it, Get Out And Look.
Just keep repeating all this and soon you will be hooked up and ready to hit the road. If it takes 5 minutes or less, great. If it takes 15 minutes, that's OK too...I've heard of newbies who can't do it in under two hours...but eventually, even THEY get it done.
Practice Practice.
Good luck!