I am an avid and prolific reader. I usually have a couple of dozen fiction books checked out of the library at a time, average reading at least two a week beyond the non-fiction and textbooks that I must read, and I'm always searching for more. So where do I look? One place is Amazon. If you have an account they love to give you recommendations based on what you've bought. And even if you don't have an account, if you go look at a book that you do like you'll see their "customers who bought this item also bought" feature.
Another tool I use is The Readers Robot although there aren't very many books there yet. It is growing, however.
The Reader's Advisor Online is for
readers' advisors and bibliophiles who work with readers. You'll find essential news, tips, fun stuff, and a community for exploring RA issues.
There are a number of these kinds of websites including Reader's Advice and the Reader's Advisory Link Farm.
The keys are knowing the collection, knowing the reader, and knowing where to look to find good recommendations if they're not right there at the tip of your fingers. There are some authors I especially enjoy and once I discover them, I devour all of their books. There are some series I like and again, I'll read every book in the series. Some I've found just by browsing. Others are recommended to me personally.
I use LibraryThing to keep track of my books and I also use that as a tool to find others using tags. I have signed up to be an Early Reviewer and have requested books, but so far I have not been one of the chosen.