To begin with your progress needs to be at corruption level or get corruption blocks from a friend, the store or other means. You will need to build a minispawner out of corruption blocks. There are plenty of tutorials, guides, videos, and people on this subject.
My setup is around a 20x20x2 deep. It’s not precise but doesn’t need to be. I like to spread the spawner more than the usual 10×10 to get a better chance of a chest but try to keep the bulk in a chunk.
In this image you can see the minispawner just north of my location.
There are two teleporters on the minispawner, one to send mobs from outside the spawner and one to send mobs from inside the spawner. These are setup in a fenced hallway with a teleporter on each end. One end of the hallway is exposed to the outside and the other end exposed to the minispawner. This way all mobs see a pathway.
There are also two traps on my safe platform, one with water(loot) and one without(tame). I can change the transporters codes to send the mobs to either trap. The traps are a good distance from the spawner but still in the same claim, or near just keep within view of anything that spawns.
The tamed mobs
The tamed mobs need to be parked somewhere behind 32 blocks from the spawner. I have my trap platform big enough to bring them to the back of the platform temporarily so to keep getting spawns.
On the above screenshot you can see by the blue dots where I left the tamed Things. Leaving them closer will lower your spawn chances. Parking them at the front edge of my safe platform stopped all spawns.
How it works
The key to getting Things is the diamond chest. Once it spawns the guardian Thing will also spawn. Do not leave the area once it spawns and do not completely loot the chest. You can take everything out but one count of one item, I usually leave a recipe if there is one. Do not make the mistake of thinking you can remove everything and place something else in, this does not work.
As long as that chest remains and you leave no pets too close you should get a thing or two or three a night.
Tips: If you have a good connection that allows quick login try this. Tame or loot the mobs that spawn. Logout of the world and then immediately log back in. If you are quick enough the chest will remain and more mobs will spawn. I regularly can tame 4 a night and if they move to the transporter quick enough I can tame 5 in one night by doing the logout/login force spawn. You can get more if you are just killing them and looting. You should get spawns up to around 4:00AM using the force spawn.