The trick, naturally, is writing a logline. And, yes, even if you're preparing a query for a novel, spending the time to develop a logline (essentially a one or two sentence summary of your story) will be worth the effort.
I cannot guarantee I can tell you how to write the best logline. But I can give you some pointers on what you need to look for.
Approach number one. Break it down by components. (NOTE: this method I only have partial notes regarding the example given by the speaker. It's a wee bit rocky in transition but should give you the basic idea.)
Title: The Matrix is an...
Genre: action-thriller about...
Character/Protagonist: a computer programmer by day, hacker by night...
Storyline/Setup: who discovers reality is just an elaborate deception...
Complications: and when pursued by agents of the the machines who control humanity...
Theme: he must find the courage to become the hero he was destined to be.
So, that's pretty straight forward. Of course figuring out your own logline is the real bitch. But trust me. Breaking it down into the individual components like that is not quite as hard as you think. The real trick is to focus on each element individually. Find the phrase that really sums up the protagonist. Figure out the essence of the complications facing him/her. Then, once you have all the parts laid out, work on fitting them together into a cohesive whole.
Remember, you want to have one or two sentences total when you're finished. And when you're finished you should have the core of your story right there. Which makes writing the rest of the query letter (I'm unpublished and seeking representation for my 80k book, etc, etc.) not nearly as difficult. At least, that's the idea.
All right. On to approach number two.
(NOTE: This info is taken from the brilliant book Save the Cat! The Last Book on Screenwriting You'll Ever Need by Blake Snyder. The genius in this approach is entirely his. Go buy his book.)
Snyder believes there are four must have elements for a killer logline.
1) Irony. This is the hook in a really good logline. Look at the example in approach number one. Neo is a computer programmer living in cubicle-ville who turns out to be a bad-ass superhero. Ironic, yes? That's the idea.
2) A compelling mental picture. The logline needs to give the reader a strong visual. Again, it's all about finding the hook. Give them something they can see. You might also think about this as giving them something to identify with, a common ground with your protagonist.
3) Audience and cost. Again, this really boils down to giving the agent/editor something to identify with. You want them to recognize your protagonist and know that he/she will appeal to a specific readership. This means finding the right details to communicate who your protagonist is and what they're about. "Cost" - which is really about location - in this case can help you pin down genre/setting. Is it a drama taking place in a small town? A thriller that covers all five continents? An action-adventure in space? Pin it down and fit it into your logline.
4) A killer title. You need to include the title in the logline and it needs to say something about the project in question. A good title will really make the logline. Why? Because a good title will likely include/accent one of the other parts of the logline.
Finally, you'll need to test your logline. Snyder tested his loglines on strangers. Seriously. Anytime they would start to lose interest, start checking their watch he'd make a mental note that was an area he needed to work on. Not all of us are that bold (although it sure beats testing them on family) but the principle is sound. Find someone and ask them if this
If you can get your story wrapped up in a single sentence or two that's all you'll need for the query. (I know they say you can do a small paragraph, but remember, less is usually more when it comes to a query.) Fill in the other information, insert the logline where appropriate and there you go.
Simple, yes? Let me know how it works out.