First of all, I don't choose books at random, so I'd make sure to look in the right section(s) of the bookstore/library. to begin with.

Now let's play a bit and pretend the books have no blurb. My first instinct would be to look for books I haven't read by an author I like.

My next instinct would be to look for authors and books I've heard good things about and haven't read yet - classics or flavours of the moment.

Another instinct would be to look for something from the more narrow-focussed publishers or collections I like. I can pretty much safely pick any title in Gallimard's Découvertes (non-fiction) if the title indicate it's a topic I care for.

Another factor could be price. If I need something to read this badly, I'll most likely look if one or the other of those I call my "time-killers" (essentially crime fiction) has got a new title in PB. Or again I will go with something in a collection (pretty much all the scandinavian crime fiction translation in French is safe enough to kill an afternoon, for instance).

Finally, my next instinct if I have nothing to read and I'm not where I can dig up something from my library would rather be to buy a magazine, likely literary mag or history mag.

As far as I'm concerned, the only thing worse than being without a book is being forced to read a bad book (objectively bad or just not to my taste, it's all the same to me). I think I'd prefer to twindle my thumbs doing nothing a whole afternoon than reading crap (which would get me in a bad mood in a way doing nothing doesn't).

The only thing title and cover art do for me is occasionally attract my attention on a book. When I wander in bookstores, which I do a lot, I will often pick up something with a really nice cover/layout (especially when it's American books, since those with decent to excellent cover art are the exception rather than the norm), or intriguing cover art. It's the same for intriguing titles (it's the title than attracted me first to "The Unbearable Lightness of Being", "Even Cowgirls Get the Blues" or "Do Androids dream of Electric Sheep?" or even "Otherland", while it's the cover that made me read the blurb of Stephenson's Cryptonomicon) . Then I'll either read the blurb or even a few pages. Most of the time I just make a note of the title and find more info about the book at home, or I look online at the bookstore. I can't really think of any book I picked at the library or bookstore just on cover art or title.

What is far more common for me is to overlook (or hesitate over a big deal) books I don't know about because of the moronic/cliché title or the really bad cover art. I've delayed for about ten years reading any post-Tolkien American fantasy because of their awful covers. It took raving personal recommendations for me to start considering to buy TEOTW by Jordan for instance (which the first time I read it I thought was as bad as its cover was ugly, as a matter of fact).

Even for blurbs, I buy more French books based just on blurbs than I buy American ones, as I find the French way of writing blurbs more reliable, while in the US it's usually just fairly pushy marketing, with tons of meaningless quotes taken out of context from reviews.