For me, having people around is quite distracting, so I wouldn't do the coffee-shop, nor the library unless it is severely underused. If I couldn't write at home I'd consider a car parked somewhere rural and invest in a thing or two with good batteries.
Time of day makes a large difference for many people. I'm most productive late when I'm somewhat tired, others like to write before breakfast. If the difference is similarly significant for you, your personal optimum should be easy to find.
severely underused
I'm not sure about 'severely', but I'm pretty sure it still has worktables (if not the desks with vision-blocking walls it used to, a piece of furniture I'm now realizing I don't know a name for) along the edges with minimal traffic.
having people around is quite distracting
In my previous coffee-shop writing endeavours, I managed to reduce said distractions by going in the evenings when there were few people, plus throwing something instrumental on some earbuds.
Time of day
A thought I hadn't considered, and should. Which is exactly the sort of thing I started this thread to evoke. :)
Yesterday, I set a personal deadline: If I haven't started writing more "S.I." by Canada Day, then I'm going to start writing up the fast-finish version of the plotline to at least tie up the story and stop having it hanging over me.
Never underestimate the power of precommitment.
Now that I've started thinking in terms of my writing more of SI as a simple fact, I've realized that, due to complicated/personal/private home-life stuff, in order to actually have a reasonable chance of even writing the short ending, I need a new low-distraction work-space, and nowhere in my home is suitable. The most likely candidates are my local public library when it's open (Tue-Sat, 10am-5/6/9pm), and, elsewhen, a particular local coffee-shop with a customer-available power outlet. And, in fact, my not noticing the lack of a suitable low-noise typing location may have induced an ugh field that kept me from even trying to catch up with suggestions and comments to SI even as my depressive episode has waned.
It occurs to me that there may be further options I'm not considering; and that there may even be other aspects to the process of writing which could be hindering my progress. And so, I come here, to inquire of the local hivemind: What advice can you offer?
For example, I currently have two and a half devices to type with: A Thinkpad laptop, an iPhone with a touchscreen keyboard, and an iPhone with a (folding) full-size Bluetooth keyboard. Should I look into some other input device?
Or: Is there some aspect of nutrition or hydration that I should pay more attention to?
Or: How significant is the audio environment? Should I pick a particular soundscape or playlist and hook up the headphones, or would there be minimal effect compared to a library's shuffling or coffeeshop's satellite radio?
Or: Would turning off my connection to the internet, save when I'm looking up some reference, be useful or annoying?