I’m sorry to answer this question in a way that may be perceived as snotty and selfish:
But almost never.
Well, if you are an aspiring novelist, you really do wonder, don’t you, when you can turn that cordial acquaintance you have with a published writer into something helpful for you? When I first started out I did wonder what the protocols were for various things: reading ms, getting advice, getting blurbs and asking for references. I’m not going to go into those other areas right now, except to say that if you have sold the ms. and are asking for a blurb, it’s ok to ask for a read. After all, I may ask you for a blurb sometimes soon. (I had a fan once who sort of attached himself to me. I quite liked him, and we had a cordial relationship, including a request for me to read his manuscript, which I did. Within two years he was far out-selling me, and if he were in my genre, I would have asked him for a blurb!) This does not give you the right to feelinsulted if the writer has no time to read the ms., of course. But you knew that.
The reason that I can’t read your manuscript is that I get a lot of requests. Some months it feels like a flood. Time is always short for writers; there are more stories than one has time to write. There is steadily increasing pressure to spend huge amounts of time in promotion, including social media and web presence. Writers are horribly underpaid for the most part, so we are always writing more things than we have time to in the hopes of maximizing our income. We long to read for pleasure, not one more ms. that one must attend to critically.
Furthermore, when an author reads your ms., you may get the unsettling reaction that she doesn’t like the story. This is uncomfortable for both the new writer and the author. The author is aware that the aspiring writer may be quite downcast by criticism; the author is aware that the aspiring writer is very likely looking for validation rather than genuine feedback. Worse, the author is aware that she may be wrong. Just because I’ve written ten novels doesn’t mean I’ll be right about questioning your concept of a psi-enabled dog who turns into a vampire hound and saves deserving children. I may hate that book, and you may be outselling me in two years.
Those of you who follow my e-newsletter on fiction writing know my conviction that it is up to the writer to critique and edit his own ms. It is your story. You can’t assign revision away, and you may not, even with the best of intentions, get helpful feedback from a published writer.
A caveat to all this: If you have a relationship with the author, then things change a bit. What do I mean by a relationship? Well, suppose you’ve done a favor for this author. . . such as set up an appearance for her or supplied some research for her work in progress. A favor deserves a return favor; but of course it is still a favor–that is, not an entitlement. Or you may have hit it off right away and had lunch a few times with her, say, at conferences; she’s asked you to lunch.
If this is sounding elitist, I’m sorry. I think it is honest and practical, given how busy all our lives really are.
And besides, there is no magic answer to getting published. Not my advice, nor Neal Stephenson’s, nor Margaret Atwood’s is going to make it happen for you. Neither my connections nor theirs is going to do more than save you a couple of steps. It’s all about the story you tell, and how you tell it. There are no shortcuts.
If there are, it certainly isn’t about a harried author’s quick read of your manuscript when they’d rather be playing scrabble with the kids or finishing their own novel.