I'm working on a synopsis right now. Unlike many a writer, I actually enjoy writing synopses, mainly because I now write them to sell a book, not after the book is written. Then it's hard to figure out what to leave in and what to leave out. As it is for me now, the synopsis is me figuring out the story before I have to write it.
Which means I'm free to do whatever the heck I want. I'm freeeee! I just go to town, knowing that I can revise it later.
So I wrote one, and now I'm revising it. I intended to trim it down a bit, but what with adding more backstory and making it very, very clear what the hero sees in the heroine that makes her different from every other woman he's met, and vice versa, it's gotten a little longer. Ah well, it's not too long (anything over twenty double-spaced pages, I worry is too long). It's at 15 now, so that's acceptable.
I can tell you what's not in there: a physical description of the heroine. All I say is that she's beautiful. For a synopsis, I think that's fine. The hero gets more description, in part because he's still suffering from the effects of imprisonment.
I don't list a whole catalgue of events. I have no idea exactly what's going to happen in the middle; I'll find out when I get there (which can mean troubles later, but this is how I've worked for years, so I don't worry too much about this lack). I am far more specific about the set-up, the meet and the ending. However, I do pinpoint the circumstances when the relationship undergoes a major change.
I keep secondary characters to a minimum. I only put in historical details if they're vital to character or plot.
Basically, I'm talking about how these two people meet, why and how they fall in love, and how they end up together, and that's it.
I'm going to read it over once more and then I hope it's off to the Big Apple. And then I'll wait to see if it's okay, just like I'm waiting to find out if I have to do revisions on the finished manuscript I sent in last month. Now that's difficult.