How do I decide which books to buy?

I was wandering my local Barnes and Noble on Sunday when I was asked this question. I thought about it. Then thought some more and realized I have no idea.

That’s only partially true. If I’m reading a series I’m enjoying, then I just continue. There’s the Amazon list of 100 books everyone should read. Sometimes there’s a ton of hype surrounding a book. Some are heavily recommended. And most rarely I’ll just find myself in the bookstore waiting for something to catch my eye. All this to say I have no set way of deciding which books to buy. This likely explains why I have so many books I haven’t yet read. I buy them in a moment of interest and then once the moment passes, so does my willingness to read them.

How do you decide which books to buy?