How do I get the heads of monsters in Minecraft?

I got his head from the wither. I try all the time to get my head off the ender or the creeper but I can't do it. How do I get the heads of monsters?

Here you will find all information about "heads in Minecraft"! https://minecraft-de.gamepedia.com/...a.com/Kopf

I would like to add that with the modification "Logical Drops Mod" you also get heads from the respective monsters!
http://www.9minecraft.net/logical-drops-mod/

You get all heads except the witherskeleton head only in creative mode or with cheats.

I don't have a single cheat active and play for survival. I have two of them

But you only have witherskeleton heads, right?

Yes

OK

You can't get the others in survival mode