There is no substitute for practice.
Over time it will become easier.
Set up prior to reverse is the key, give yourself as much space as you possibly can and get the truck as straight as you can before you reverse. I say straight, what I mean is as straight into the bay as you can, not truck and trailer in line.
On a triple axle trailer the trailer will pivot on the middle axle. So use that as your marker.
Blindside reversing is a pain in the a$$. Some are good at it, other not so good. I’m in the not so good bracket. So I’ll always try and turn the truck round so I can reverse from the driver’s side. Even if it means doing a 180 in the yard.
Take your time and if needs be ask someone to guide you in. Most drivers will happily oblige. If you are on your own then don’t worry about getting out the cab several times to check you are clear. One thing I always tell myself is: If you think you are close to something and have a doubt if you’re going to hit something, get out and check. I’ve reversed numerous times and had the feeling I’m taking a risk, usually because I am, and when I haven’t checked I’m clear I’ve hit stuff.
If it takes you 10 shunts to get in, then so be it. 10 Shunts is less embarrassing than hitting the truck by the side of you.
Take your time and get to know the kit you are driving. Volvo’s are great for reversing IMO, because they have a great gearbox. Scanias are not so good IMO, because the gearbox is a bit jerky. Same as MAN, Iveco and Merc (IMO). If your truck has crawler option, use it.
Check your mirrors all the time. Things will appear that you didn’t see a few seconds earlier.
Finally, don’t overthink the steering. I used to find when I thought about which way to turn the wheel it would usually be wrong. It becomes second nature after a while and you just do it from muscle memory.
Don’t panic Captain Mainwaring!!