Well first I look at the cover. I know it's not good to judge a book by it's cover as the saying goes but I can't stand it when they put pictures of the characters on the cover. It doesn't leave anything to the imagination that way...and it seems a little corny in my opinion. After I see about that I look in the summary and then I decide whether it looks good or not from there.
If I still can't make up my mind after that then I read a few pages and see if it draws me in.
I always get my books from the library first before buying them unless the author has never let me down before then I can buy blindly.