I'm playing vanilla Minecraft, and am getting ready to head to the end. I need Eyes of Ender (and hence Ender Pearls), and in my main hunting grounds (a large desert area) as little as one Enderman may spawn per night. Is there any way to "promote" Enderman spawning so I can get pearls more quickly?
Endermen require a 3x1x1 space to spawn and a light level of 7 or less. The darker the place the more likely it is to spawn, the only way to decrease spawn rates it to light up/fill in areas.
Ways to increase Endermen spawning in particular include stopping spiders or slimes from spawning instead by filling in areas below level 40 in slime-spawning chunks. Also get rid of 1x2x2 areas for spiders to spawn. You will still get normal levels of the other tall mobs (skeleton, zombie, creeper), but they do not have any unique spawning requirements so nothing can be done.
Using a sword with a looting enchantment with give you more enderpearls per Enderman. And going to The End will mean only endermen can spawn.
If you're standing in the middle of a 40 square desert, a good third of that is not spawnable due to your presence.
Also be aware of the spawning caps. Apparently there's a limit of 70-80 hostile mobs (many of which may be underground.
Try this: before night, go up into the sky to at least ~100 blocks above your desert. This should despawn the underground. As night falls, go back down to an altitude of ~20-25 blocks. This should keep the influence of your presence to a minimum on the ground level. If you see more than 50 enemies, either kill or despawn them to stay below cap.
I have built a farm where my spawning platform is 1 block wide so no spiders can spawn on it. I have a sticky piston at block 2 which occasionally (about once ever 10 seconds or so) will push in and sufficate skeletons and zombies, the endermen will survive this, so in theory over time only endermen will be in the trap. I've only JUST built it and haven't given it a good testing, but the theory is reasonable I think.
There is a good way if you have block types other than dirt (dirt will NOT work due to Endermen picking it up). You can do it underground and I advise you to do so due to possibility of gaining ores and loot. Anyway what you do is flatten a big area and build a 4 block high wall around it. Then you need to cover the roof up with material of choice (other than dirt). Make a door at 1 side and you have a mob farm (under method) you can also hollow an underground one 3 tall.
You can also place a block get on top and look for black heads!