The spell Locate Creature says you can find a creature of a specific kind, but not one of a specific type. I get the whole type/subtype classification, but I can't find any definition of kind. What sort of category can I search for with this spell?
Locate Creature states:
The spell can locate a creature of a specific kind or a specific creature known to you. It cannot find a creature of a certain type. To find a kind of creature, you must have seen such a creature up close (within 30 feet) at least once. Pathfinder PFD
While Creature type is game defined, kind is not, so we refer to plain English.
Merriam-Webster defines Kind as:
a specific or recognized variety
Thus you can specify dire wolf, elf, red dragon but not beast, humanoid or dragon(type).
So far as I'm aware, Pathfinder never formally defines kind like Dungeons & Dragons 3.5—the game that it's based on—does. In that earlier game, kind means, "A subcategory of creature type. For example, giant is a creature type, and hill giant is a kind of giant" (Player's Handbook 310).
Likewise, Pathfinder, as it's based on the Dungeons & Dragons 3.5 SRD, couldn't include from its forebear's Player's Handbook the actual published examples from that earlier game's spell: "The spell can locate a creature of a specific kind (such as a human or a unicorn) or a specific creature known to you. It cannot find a creature of a certain type (such as humanoid or animal)" (249 yet parenthetical examples absent from both the SRD's locate creature spell and the corresponding locate creature spell in Pathfinder).
With that in mind, this Pathfinder GM has ruled that a locate creature spell in Pathfinder works like it does in D&D 3.5. That is, the spell can be used to find a creature by its initial entry in the text where it's found—essentially, by its common name. That is, the spell is able to find, for example, a black shuck, balor, or adamantine golem, but, respectively, the spell can't be used to find just any old magical beast; can't locate only a demon, outsider, or creature that possesses the subtype chaotic, evil, or extraplanar; and won't seek out simply a construct or a golem.