Title giveaway
Titles are hard.
However, this does not mean that the title of your story should provide information that doesn't appear in the story itself until the surprise climax.
For example, if you're writing that hoary old story in which a person gets a visit from a beloved old relative, and then after the relative leaves the protagonist discovers that the relative died the previous day, it would be best not to title your story "A Message from the Grave."
I know this seems obvious when I put it like that, but we get a fair number of stories—maybe two or three a month, maybe a little more—that aren't badly written, but that give away the central surprise of the story in the title.
We tend not to like surprise endings anyway, so it doesn't tend to make a difference in whether we're interested in the story. But it might make a difference elsewhere.
Maybe this is the way to go: tell your title to someone well-versed in the genre of your story. Ask them to guess what they think the story's about. If their answer is something you don't want the reader (or editor) to know 'til two-thirds through, consider changing the title.
This public service announcement was not sparked by any story in particular; just something I've been thinking about.