I have a tendency to literally judge a book by its cover. The title is very important, and what tends to draw me in in the first place. If the title doesn't catch me, I'm unlikely to read. Then there's the description and the rating. I rarely read anything below mature rating unless the description and title have really drawn me in. Lastly, there's length. I'm more likely to read a short story than a novel at the moment, simply because reading novels is very time consuming. So if I'm looking through an author's works for something to read, I'll generally start with a short story or novella of less than 20,000 words. Then, if I really like what I see, I'll move on and read the longer stuff.
If it is poorly written, I'll probably put it away again, unless the plot is exceptionally good, because the beta/editor in me will point out every little mistake to me and I'll get really annoyed. If the plot is good enough, I can sometimes get past that, but then we're talking tremendously good.