My approach to the bookstore is strictly alphabetical: I go to the A shelf of the Fiction section and skim every single spine; interesting titles will be picked up and have the blurb read if the cover is equally compelling; if I like the blurb I'll read a sample chapter or two and take it from there.
New books by authors I adore will be added to the pile in my arms almost indiscriminately and clearly authors or titles that have been recommended to me by a reputable source (i.e. someone on here as opposed to Richard & Judy) are going to jump out at me; however I do try to give everyone their fair chance by allowing each and every book to inspire me on the spot.
That, of course, is why I consider an hour in a bookstore to be a rushed visit.
Incidentally, I am an unpublished writer myself so I'm the last person to want to discriminate against lesser known authors. My suggestion to grab the kind of readers that really matter (i.e. discerning and loyal ones) is to have an intriguing title and an unusual, pretty cover. While I don't judge books by their authors' names, I do tend to judge them by their title and cover, for they oh-so-often accurately reflect what's on the inside.