I voted "Other" as a stand-in for "The Library", because that's how I get the overwhelming majority of the books that I try, and am usually introduced to 80%+ of the new-to-me authors I haven't read before (and interesting non-fiction subject matter) whom I then go on to buy my own copy of if I happen to enjoy them enough.
I check out the New Books Shelf* regularly, sometimes pick up from the librarian-assembled theme displays and recommendation listings, semi-randomly sample interesting-looking stuff from authors/subjects which happen to be filed very close to titles I've been specifically looking for already, and very often go back to get other books from authors I've tried and liked using the above methods.
The used bookstore and discount sale table also occupy a similar niche, but a narrower section thereof, because a book has to be really promising or extremely cheap (and interesting-looking) before I'll shell out for it if it doesn't already cover one of my pet subject areas or belong to one of my favourite sub-genres.
And from there I go on to get the e-books if they happen to be available at a decent price (okay, really cheap on sale).
I'm actually really bad at browsing for new e-books and tend to go by backlists of established fiction authors whom I know to have a decent reputation and have tried at least one of their works (or they've won an award), and perusing the catalogues of e-publishers which specialize in reprinting such, though occasionally I have picked up totally new authors from reading the promotional giveaway freebies.
* The "New Arrivals" section of the library's e-book catalogue gets treated the same way and I wishlist anything which looks even remotely interesting and put holds on the most promising-looking stuff.
But frankly, if a particular e-book title is available through the library, I tend not to buy a copy and instead focus on picking up another non-library-available work by the same author.
Last edited by ATDrake; 09-19-2011 at 08:50 PM.
Reason: Elaborate, since this is for e-books, not just print, although the methodology is almost completely the same.