These traps are widely used to trap mobs in a hole in the ground. usually creepers all, but a wide variety of other mobs may appear in the trap. Don't expect spiders, though. They can climb walls.
Step 1: Create the Hole
I made mine out of an accidental creeper crater, but you can make an intentional hole by digging. But, honestly? It's easier with the creeper crater. Once. you have the crater, dig out any steps there are that monsters could use to jump out, then raise the sides so it's harder for you to fall in. Keep any chickens that fall in there, though. Egg supply.
Step 2: Build an Overhang.
This OverHang should cover the entire pit (only the pit). This roof stops skeletons and zombies from burning in the sunlight when they fall in there.
Step 3: How to Get Out?
When you are stuck in the trap after collecting your kills, how do you get out? You build up! (Don't worry - That's not Herobrine, it's just my skin).