I usually ask close friends whom I usually trade books with. I know they have a similar aesthetic, are essentially my target audience, and I email the current draft to them with instructions to take a hatchet to it if necessary. If you're very specific with what you want, that helps. I have one friend that I tell to ignore the spelling and grammatical mistakes, and to alert me to odd jumps in plot where they feel jerked around too much, to discrepancies in minute details (names, places, colors, etc), and to overall feeling: Did this answer your questions about x? Was that how you expected the situation to resolve? Did anything seem out of character with what you've read so far? Etc.
I have another friend who is my grammar man. He corrects spelling and flags jumpy and choppy language.