It is a little strange to ask, but are there ways to get feedback from friends about the quality of fictional writing (whether they liked it, not more objective aspects like spelling/grammar/etc.) unbiased by the friendship that is likely to bias the judgment?
Choose your friends wisely! I started with a group of ten friends when I first started writing who had volunteered as beta readers. Five responded very quickly that they really loved my first book, even though I felt it still needed a lot of work. Three more came back a week or more later with glowing remarks. The last two took at least a couple more weeks, but both of them came back to me with questions, suggestions, and criticisms. Guess which ones are still beta readers five books later?
Make sure you tell your "friends" that you are looking for true, honest feedback. Tell them that they are not going to hurt your feelings (although in my case that turned out to be wrong, but I ultimately agreed with the criticism). Let them know that you truly NEED constructive criticism or feedback or suggestions and you need it to be brutally honest. Lastly, make sure you choose people that already read your genre (that was a mistake for me with two people who later admitted they really didn't read much of the first book).
Because they are your friends, their first inclination is going to be to encourage you and reinforce you, even if it means lying to you to not hurt your feelings. If a friend is willing to tell you the truth, even when they know it will disappoint you, then that is a friend you can trust!
Share your work as a revision-enabled word processor document (e.g. Word) or a cloud service (e.g. Google Docs):
Tell them to assume that they're reading an actual book that they paid money for. Tell them you already have positive comments and that you're looking for the flip side:
Choose beta readers who read regularly. Better if you've heard them talk about other authors' works in the past
As a final note. I did all these recently and it worked out very well. (It didn't hurt that I had several well-read friends with absurdly high standards!)
I like to listen to how people reacted to my writing. Frankly, I don't care what their suggestions are. They are reading your book, and I think they should act as a reader does, not as a writer. Feedback such as:
This is feedback I like because it gives me an honest impression from the reader. They didn't understand, like or find meaning about something, and this will be different for each reader. My readers find positive things about parts and areas that I never found to be a big deal, so I focused on it a little bit more.
Conversely I think the following kind of feedback is limited in how it can help:
The most helpful advice I have gotten is from people who have simply told me what they think of the story, not what they think should be in the story.
"What do you think?"
"What do you think it should be?"
These are two very different questions. The second question can go bad very quickly. If the person gives you genuine answers about the first question you can say, "Well that's their impression, and everyone has a different one". No hurt feelings, and even better, a look into what your audience is thinking.
I agree with the above comment that first off, you need to make it clear that advice and criticism are what you want, rather than affirmation. You also need to make sure that that's actually true; many writers find it harder to discuss their work critically than they expect to. And nothing kills a writing workshop/beta faster than having the author get touchy or mount a defence in response to each criticism.
On a practical level, I would suggest you ask for your friends' thoughts on specific aspects of your work that you already have doubts about or want comments on--say, 'did this scene work for you?' or 'do you care about this character as a person?'
Also, you can present them with specific questions about what they think makes a story good/worth reading, and then ask them how well your piece lives up to that. Basically, the more you give your friends a concrete set of criterion with which to assess your story (or make them come up with one on their own) the easier they'll find it to give you solid feedback.