I own 5 different trailers. Keeping a trailer straight is actually the hardest part. The trailer will naturally turn one way or the other. Controlling or forcing this turning is where beginners fail. A thing I do to that helps me keep my trailers straight is use a feature on the trailer that is approx the width of the tow vehicle. Find a feature that allows.you to judge how straight the trailer is. I keep that feature in line with my tow vehicle and it's easier to judge when things are starting to get missalighned (I use mirrors). My utility trailer, its the sides. My Jon boat its the fenders. My snowmobile trlr, it's the tires underneath. Learn to keep the trailer straight, and turning shouldn't be difficult. For turning, just allow the trailer to turn naturally once you 'bump' it in the direction you want it to go. But you control how sharp it turns. Small inputs is all it takes. Don't over compensate. Just watch how you trailer reacts. If things go aray, just pull up enough to get it back in control. A trailer can get turned to a point where no amount of input will bring it back. Pull up a just enough to bring it back into compliance. I gringe watching videos when people get a little out of sorts and pull all the way up to start their mistakes all over. As mentioned, u haul trailers are a great option. They are fairly easy to control. Don't get a small one though. And also mentioned, an empty lot with lines to use as referance marks is a great idea. Or put markers down for referance. Start with a plan, and start the trailer in best possible position for execution.
Now for a little bragging. A few years ago, I had to evacuate my daughter from Florida during a hurricane. I hooked my 10x5 utility trailer to haul her and her motorcycle out. When we got to a hotel in Geogia at 3:00 am, there were only 2 open spots left. (Side by side). My daughter was not going to allow me park her bike any where else, out of sight. So I backed into that double space, allowing the trailer to jack knife into the adjacent space on my blind side. I did get out a few times to verify I wasn't going to crimp my trailer into my bumper. I quickly learned I could bring the trailer all the way around and the deck would hit my tire before my tongue would hit my bumper. That's how far I was jack knifing the trailer into that double space. Wish I still had the pictures to post. After a week at the hotel, I got good at parking this way. So much so, that when we were ready leave and load the bike back up. I jacked knife the trailer 90 degrees up against a side walk curb becasue the curb was level with my tilt deck. I got square and less than an inch with a few adjustments.
Another time when renting a Uhaul 6x16 we were moving my daughter and she said we had to unload in a parking garage. Part of me was almost looking forward to having to back down a few levels to get out of the garage. My disappointment when we pulled into this huge loading dock area. Cocky, I know. But in theory, if you can pull in. You can back out.