I've been trying really hard to get ender pearls but the problem's that I can't find any enderman in my survival world. I already built two towers in different locations that people said were the best spots: one in the plains and another in the middle of the desert, no water around, and still, they just don't spawn. I wonder if there's something wrong with my game, or maybe is it some bug from Biomes O' Plenty? I really would appreciate some tips.
If cheats/commands are enabled in your world, you could try typing "/testfor @e[type=enderman,r=150]" to see if there are any endermen within a 150 block radius of you to see if they not spawning at all, or just spawning in remote locations.
You'd have better luck running around in the desert or plains to cover as large an area as possible.
Bring a good bow and a lot of arrows if you don't have Infinity on it so you can pick off the skeletons and creepers from a distance if you can't bypass them. Wear good armor and bring a whole stack of food, healing potions if you have brewing, a few milk buckets for witches and you might want to prepare by building a few huts to go to if you need time to heal.
I'd say the main benefit of plains and even more so deserts is the visibility, it's easy to see the mobs and pick your fights or pick mobs off at a distance.