Yay! A new question and a good one too!
Personally, I think the summary is always the hardest thing for me to write. I spend way too long thinking about it. I'm not a big fan of giving too much away. I hate when I feel like I don't need to read a story because the summary just basically told me exactly what was going to happen but at the other end of the spectrum, I tend to shy away from stories that give a really vague summary and get annoyed when they give a misleading one.
I think if you have a major plot twist in the story, to keep it authentic, and a real twist you shouldn't give anything away in the summary, except maybe to say there are some twists and turns along the way. The thing is, if you really are going in a completely different direction then what the reader may think, and it's written really well, the reader will still follow along. You can always say something like "Things aren't always as they seem." maybe not as cliched as that, but you know what I mean?
I'm about to start posting a new story myself but the thing that's really keeping me from doing it is the stupid summary as well lol Seriously, it's my real weakness. I need a course like summary 101 or something.