Runs with scissors discussion

This topic came up in another group I'm in, and it got me to thinking about how and why we rate our books the way we do. I rate most at a 4 or 5 stars, and reserve 1 and 2 stars for books that I really didn't like. I do not have a criteria for rating, as some do, I go based on a book to book basis, mostly on how the book made me feel at the end, if I want to read more by that author or if I thought they should be burned in effigy.

I also take time to review all my books and I do rate books I do not finish, if I get beyond a certain point, which I reflect in my review as well.

So, do any of you have guidelines for how you rate a book?

I generally center around 3-4 stars. 1-2 star ratings are, to me, just awful, though 2 stars could mean it just didn't engage my attention enough to care. 5 stars are reserved for books that got a strong (positive) emotional response from me, be it nostalgic or character or story based.

If I don't finish a book, I don't keep it on my shelves; it's not really fair to rate a book I didn't even read.

I always give 3-5 ratings. If I don't like a book at all I don't bother commenting on it - or I simply don't finish reading it. There are plenty of books that I am only a little engaged in that I do finish, so I might give those a three.
I suppose this is problem though, books that don't get rated at all could either be very bad or very unknown.

I think that rating is personal on that point. If a book is that bad, it should be rated a one (I wish we had half stars!) I too will quit a book if it does not engage me. although there have been ones I kept reading waiting for SOMETHING to happen....