For your second question, I do both, and I'll do it both in person and online! For your initial question, there would need to be something that catches my eye. Usually it boils down to one (or more) of these three things: eye-catching cover, intriguing title/subtitle, and the quality of the reviews/ratings. (Ratings and reviews are obviously easier to see while browsing online, but I will look up the book online when I'm in a physical store to see what their ratings/reviews look like.)

Hi Rob, have you checked out Kit? We recommend this for our authors, and they're actually one of our affiliates too. You can access their website here