I know this might sound crazy, but whenever I go into a bookstore and there's so many books to read, what I usually do is, instead of paying much attention to the reviews or synopses on the back, I read the opening sentence of the book. From that, I can tell if I want to read the book or not.
This isn't exactly a technique, but do you ever find yourself judging a book not from its cover, but from its first line? The books I don't want to read, the mediocre books, usually have a bland opening like, "It was raining in [insert city name here]" and is usually some short, abrupt sentence which tries to grab your attention. Bad crime novels and thrillers and other "popular" genre books are often like that. Whatever happened to opening with something more witty, enticing, graceful, controlled, and at the same time, gripping and unexpected?
For example, the novel which grabbed my attention from its first line and made me want to read it right away was Orwell's Nineteen Eighty Four: "It was a bright cold day in April, and the clocks were striking thirteen."
Tell me that ain't cool!