One part of my personal answer is to start a lot more books than I finish.
Another is that I read signed major media book reviews -- the kind where the review author gets paid (I know not enough). Here are some web sites to try:
http://realclearbooks.com/
http://www.nybooks.com/
http://www.lrb.co.uk/
http://www.nytimes.com/pages/books/review/
The last three above are available for your eReader via the Calibre Fetch News feature.
I also get interested in a subject (lately, 20th century Taiwan history) and search out books on it at libraries or via googling. But before reading, I try to find at least one review from a reliable source.
Lastly, I do sometimes bring up the Overdrive collection at libraries I have cards for, and search in categories that interest me for books added in the last so many days.
One thing I really do want is an equivalent of RottenTomatoes.com for books. Since the ratio of professionally edited reviews to books is so much lower than the ratio of reviews to films, a book review tabulation site could never be as apparently fabulous (apparently, because I hardly watch movies) as rottentomatoes.com. But someone should try.