Maybe it's the artist in me, but I've always had a thing for good cover art on a book. It's the first thing I notice when browsing. And paranormal romance novels have some of the most kick-ass covers. I picked this one 'cuz not only is it a beautiful cover (I love purple), but it is an awesome series. I generally don't pick books that have yellow covers because that color offends me for some reason.
If the cover grabs me I read the blurb on the back to see if it does the same. Unless it's one of my favorites, author recommendations mean nothing to me. It's all about the back cover synopsis. If it's confusing or boring, I put it back.
Unfortunately I can't name specific things that make me go, "YES!" But a few things that will turn me off are:
A.) love triangles. I think it's because I've been in one or two (Loooong ago) and the emotional baggage of them nauseates me.
B.) If the heroine/hero has a kid/kids. Harsh, I know. But as a mom, I read to escape. (One major exception is Rebecca Zanetti's DARK PROTECTOR series.)
C.) Getting back with an ex. This one's 50/50 for me. If it sounds like the back story will be told and it's interesting, I may give it a whirl. Because one of my favorite parts of a romance novel is reading about how the characters first meet.
Of course I can still be willing to read these types of romances if they come recommended by friends or are by a well-loved author.
How about you? What grabs you in a book's cover art and blurb. What things make you go, "meh," and put it back on the shelf?