Anyone know how to make a name tag in minecraft?

The real reason to bother with them: a named mob never despawns. So a villager you dragged home or a horse you like, put a name on it and it's safe. Right click the mob with the tag in your hand once you've named it on the anvil. jeb_ gives you a rainbow sheep, while we're doing joke names.

Easiest is librarian villagers, a master level one sells them for emeralds. Otherwise fishing or dungeon/mineshaft chests, which is pure luck. Then you need an anvil to type the name onto it, costs a level. Name it Dinnerbone if you want a laugh.