I would write how we say in general. (In some poet or something, it may be changed by authors or speakers.) - Demons いる - Ghosts いる - Vampires いる - Zombies いる - Plants ある - Feet ある - Hands ある - Viruses いる and ある - The universe ある I hope this helps you.

this sounds like a strange method, but what i like to do when i am unsure about which word to use, i do a quick check in my google search bar, and usually the commonly asked quesiton/used phrase will appear. here is what i mean: http://imgur.com/OClU88Y http://imgur.com/a3tthBV that method helps me a lot when i feel like i need to make a quick judgment. of course it's always best to refer to a native speaker of that language. hope it helps, though!