The pitch includes your character, what they want in the story (or what they want to avoid), who/what is standing in their way, where and when it takes place and what makes this project special. Holly Lisle calls this the sentence. The folks at Writing Excuses call it the elevator pitch. However you want to think about it, having your story boiled down to one knockout sentence before you start writing is key to keeping on track. Even those that frown on making outlines or doing other prep work, concerned that it sucks the fun and magic out of the process, should be able to put their idea into one sentence. This is the bare minimum and boy can it be fun. It doesn’t have to be perfect right now though. Don’t let making your pitch perfect get in the way of moving on to the writing.
So how do you do it? There are a few ways. Holly’s method is define your protagonist in two words (strong adjective, strong noun) like empathic superhero. Then define your antagonist in two words (strong adjective, strong noun) like psychopathic superhero. Next define your conflict between the two. Know your protagonist’s need and make it a part of the conflict like needs to stop the antagonist before he kills again. Next define your setting like aftermath of the destructive heroes war and then finally the twist. Which is why you are writing this book and not something else. My twist is before he becomes what he most fears, a super-villain. So my whole sentence would read:
After the destructive heroes war, an empathic superhero needs to stop the psychopathic superhero who killed his parents before the vigilante kills again and before he becomes what he most fears, a super-villain.
That’s just the rough sentence, you can tweak it until it sounds great. If Holly’s method works for you, check out the rest of her site and consider joining her boot camp forums. She’s a wonderful teacher.
Another way is to use the LOCK method by James Scott Bell. LOCK stands for Lead with Objective against Confrontation with a Knockout ending. So my lead is an empathic superhero who wants to stop the killings of retired super-villains after his parent’s murder. The antagonist wants to keep on killing in order to both protect the world from the more dangerous criminals and to sate a hunger he can’t any other way. The knockout is when these two face each other head to head, both wanting similar things (protect innocents) but go about it in ways that are counter to each other. Can they find a common ground or can only one of them survive to continue things their way?
The above is not a sentence, obviously but from that you can usually boil it down. You have all the elements in front of you.
Finally an elevator pitch is to take two different ideas and mash them together, usually in a pithy sentence. Sometimes this looks like this + this = my story. One example is Mary Robinette Kowal’s Shades of Milk and Honey which is Jane Austen with magic. Something that interests the listener/reader and gets their mind to ask questions.
Hope some of this helps with coming up with your own pitches!