- In your dreams you think, "This would make an awesome story." (Although usually the dream is about something stupid, like talking zebras.)
- You look in bookstores/libraries for the place on the bookshelf where your book would be if it were published. (At my local library it'd be between a book called A Taste for Quiet and a collection of short stories called Gothic!)
- You say to your sister, "I need a stupid boyfriend name and a bunch of gay guy names" and she automatically gives suggestions without questioning.
- You're talking to your writer friend in public and say something like, "I don't know, I might kill him. I just have to think of a good way to do it." And then you realize the people around you don't know you're talking about a fictional person.
- When someone asks you, "So how's that book you're reading?" you give them a long speech analyzing the plot and characters that they really don't want to hear.
- ... But when someone asks you, "How's that book you're writing?" you respond by banging your head against the closest inanimate object––preferably against something large and solid like a wall or a table. Or you burst into tears. Or you do both.
- Whenever you watch movies/TV you're always on the lookout for actors/actresses who look like your characters.
- Your computer is full of documents containing stories, outlines, and character inventories.
- Everything inspires you––people, places, songs, books, movies, photographs, paintings, plants, animals ... Heck, LIFE inspires you!
- You write because you exist.
So, tell me. How else do you know you're a writer? :)