Some of those generalities are obvious. Spelling, grammar, and such.
You'd think they'd be obvious, but they're not. At least, not to the people who are responsible for many of the self-published books I've been sent for review.
Going from obtuse to okay is probably reasonably simple for the DIY crowd.
Based purely on the books I've been sent for review, you're once again overestimating the skill level out there.
The trick is going from okay to good, and that's where I think generalities are hard to apply and real nuts and bolts examples work better. So, unfortunately, not available from you but I'll keep looking.
Assuming that appropriate grammar, spelling and punctuation is within a self-published author's capablities, there is one really basic point which, if considered, would straight away improve the quality and effectiveness of their books' back cover copy, product information, blurb, or whatever you want to call it.
This copy is a sales tool. Its function is to catch the readers' attention enough to make them lay out some hard cash and buy the book. To do this, it has to be clear; interesting-exciting-fascinating-enticing or what ever word is appropriate for the book concerned; and for a novel (here's the biggie),
it has to tell the reader about the story.
Most of the blurbs I've seen on self-published books don't do that. They tell me little or nothing about the story. Instead they might tell me about the author, which is nice but unless the author is famous, notorious, hugely successful in some pertinent way, or has written an autobiography, this isn't the right place for me to hear about the author. I don't want to know what their career path has been, what their aspirations are, what religion they are, what their family life is, or what the author's moral or political convictions, aspirations or dreams are.
I want to find out about the story.
Nor should the back cover copy tell me about how the book was written; why the book was written; or how it came to be written.
It should tell me about the story.
The back cover copy certainly shouldn't lecture me on how capitalism is failing, or how readers need to be educated (yes, I've seen that one a couple of times); it shouldn't tell me that I need to read the book. It should grab my attention by being fascinating, intriguing, and so on, and
it should tell me about the story.
The back cover copy certainly shouldn't consist of lots of quotes from people I've never heard of which tell me how great the story is.
It should tell me about the story.
Not only should the blurb tell me about the story, it should do so in a clear, comprehensible way, it should be concise and attention-grabbing and it should all be properly spelled, punctuated and so on.
If you think this is too obvious go to my review blog and take a look at all the books I review. I quote the back cover copy in full in each review. How many of them focus on telling me about the story in a tight, exciting, intriguing way, and don't contain any distractions? I've mentioned a few of them above, but there are plenty of others.
Compare those blurbs to those of trade-published books. See the difference. It's huge.