I just discussed a lot of this with a male friend yesterday who was in a very one-sided "relationship" a year ago that he still isn't over, so these are fresh in my mind... (I put relationship in quotes because she never specifically agreed to be exclusive)
Green light: What you said, plus she touches me a lot (not sexually, I mean like she touches my arm when she talks to me or gives me long hugs, or good old fashioned childlike rough-housing), or she asks me a "buying question" (for example: "Where do you see 'us' going?" or something like that), acts goofy and silly and confused around me
Red light: I have to put in all the effort to see her, talk to her, hang out with her etc, she never calls me, she acts like she's too busy for me, acts bored by me, she makes no effort to add to the conversation, always the first to end conversations or say "I gotta go", she talks about how happy the single life is for her, she talks about not being ready for a relationship, or she just does something crazy in general (acts very interested one minute, then completely disinterested the next)