How To Write A Summary
I see many fanfics with summaries like "Summary sucks plz read" or "I cant write summaries, just read the story" or "story not as bad as summary".
Anyone can tell you that the summary is less important than the story itself, but a good summary does go a long way in making your story sound interesting and encouraging more readers to check it out. Because the summary is something that the author writes, like the story itself is, the fact that a single-paragraph summary may be poorly written doesn't bode well for the story it is attached to.
Although I make no claims that I am especially good at writing summaries, I do know a few things that have proved helpful to me while writing them for my own stories, and I believe that other writers might be able to benefit a little from what I've figured out. At least, hopefully it will give some the confidence to not feel the need to apologize for a sucky summary when they post their stories on the web.
Writing a good summary doesn't have to be difficult. All a summary needs to do is give a brief outline of what the story it is attached to is about. As a writer, you should already know what the plot of your story is, so that first step should be easy for you.
For a hypothetical example, say that I have just written a Star Wars Alternate Universe fanfic. In my fanfic, Princess Leia is kidnapped by a Cad Bane lookalike before she could be captured by Darth Vader, and Darth Vader must go off and try to rescue her in order to get the information he wants regarding the stolen plans. Fortunately Leia is as resourceful and independent as her mother, and while Darth Vader duels Bane's doppelganger she steals the lookalike bounty hunter's ship and gets away safely, for a happy end where she is reunited with Luke Skywalker and Han Solo.
That is the basic layout of the entire plot, minus any minor twists or side-plots. Because the summary is meant to give potential readers the gyst of a story, this kind of sketch makes a good starting point to build on. But, of course, we don't want to tell a reader the whole plot—we want them to read the story in order to find out what happens. We want there to be a little mystery to make the story sound intriguing.
There are two "mystery points" in the fanfic example that need to be excluded from the summary, or else they will spoil the surprise. The first, and most important, regards the story's conclusion. I might truncate the description to about here:
Princess Leia is kidnapped by a Cad Bane lookalike before she could be captured by Darth Vader, and Darth Vader must go off and try to rescue her in order to get the information he wants regarding the stolen plans.
The second "mystery point" is the identity of the bounty hunter: he isn't Cad Bane, only a lookalike, but part of the plot revolves around the fact that Vader doesn't know this and it seems the bounty hunter he killed has come back to haunt him. So next I need to restructure what I already have to account for this:
Princess Leia has been kidnapped by a bounty hunter claiming to be Cad Bane. Darth Vader must track the bounty hunter down if he wishes to get the information regarding the stolen plans.
This principle forms the basis for the most formulaic method of creating a summary, but it remains one of the most effective so long as you don't overdo it. What I have above is already the bare-bones of a summary, taking the story's plot without the resolution and limiting it to what is known from the point of view used inside the story. It could almost pass as a finished summary, but it sounds a little flat. In order to make it sound better, I'm going to make two changes.
First, I will combine both sentences to make the cause and effect clear.
Second, I'm going ot restructure the last sentence into a semi-rhetorical question, to show where the story's conflict lies:
When Princess Leia is kidnapped by a bounty hunter claiming to be Cad Bane, it becomes Darth Vader's mission to track them down. Will he find the truth behind the bounty hunter's reappearance, and recover the Princess and the stolen plans?
I say that this method is "formulaic" because there are a million stories with summaries just like this—go to any category on FanFiction.Net and you will probably see at least two on the first page that have the same structure. The reason it is so commonplace is twofold: firstly because it works, and second because no two stories (should) ever have summaries that sound alike, because the summary is based directly on the story's plot.
Remember not to overindulge yourself when it comes to mysterious summaries. As a general rule, plot conclusions should not be revealed, and anything that is a mystery the main character(s) have to solve (like the identity of the "monster" in a Scooby Doo fanfic) is fair game for this tactic. Don't make it seem that a certain part of the story is a mystery when it really isn't—if you try to build mystery around something that is revealed easily as a simple fact later on, your readers will feel baited, and your writing will seem amateurish.
Of course, just using a formula won't automatically give you great-sounding summaries. But it's a starting point from which you can learn to develop your "summary voice", just as you learn to develop your narrator's voice.
Experiment, extrapolate and have fun!