I approach the manner in 2 different ways depending on who I'm talking to/who's asking:
Someone I'm friends with (or like creator acquaintances I'm comfortable discussing projects with):
I honestly don't have any qualms about spoiling my stories to people in this group unless they request to remain unspoiled which I don't mind accommodating (although I admittedly have yet to encounter this, all of my friends are happy to talk deets hahah). For me, at least, having people to talk to and bounce ideas off of help me to develop the story into a stronger end result, especially in the outlining and scripting stages. For TreasureHUNT!!, for example, I sent the entire storyboard out to several of art and non-art friends asking for feedback before I got started on the story proper, so there were several people who had the whole short story's plot and events front to back before I even began drawing it for real xD
Misc. People I don't know and/or random readers commenting and posing questions or whatever:
For people I don't know or who are purely readers of my story I just... don't talk spoilers and answer any spolier digging questions in a vague manner lol. I think it's easier to control myself on this because I allow myself to have the aforementioned outlets. This includes anything I write or type out publicly though- like I make an exception on these forums since it's primarily a creator based platform, but generally I try to keep spoilery story discussion for my projects either in like discord servers, vocally when hanging out with someone, etc.