Continent is my favourite. Habitat is also good.
I think, to the more knowledgeable zoo-goers is layout by family (like cats in one department, parrots in one department etc.) also good. This way, you can take a quick look at your favourite animals if you don't have so much time left.
If the zoo doesn't seem like a messy building site, I'm also fine with a random order. The bad thing about dividing the zoo in continents is that it can get pretty predictable - in most Australia areas you are sure in advance to see kangaroos/wallabies, emus and maybe a kookaburra or some other bird. It ruins much of the surprise element. If you see an emu exhibit between an ocelot and a jackass penguin, it becomes more interesting because you never saw it coming.
I think, to the more knowledgeable zoo-goers is layout by family (like cats in one department, parrots in one department etc.) also good. This way, you can take a quick look at your favourite animals if you don't have so much time left.
If the zoo doesn't seem like a messy building site, I'm also fine with a random order. The bad thing about dividing the zoo in continents is that it can get pretty predictable - in most Australia areas you are sure in advance to see kangaroos/wallabies, emus and maybe a kookaburra or some other bird. It ruins much of the surprise element. If you see an emu exhibit between an ocelot and a jackass penguin, it becomes more interesting because you never saw it coming.