Here are a few more basic tips for those of you in the query trenches.
1. Use long, convoluted sentences. It does not make you sound clever, half the time; instead, it makes you sound like you are TRYING to be clever. If your query is clear enough and interesting enough to intrigue a sleep-deprived intern, you're good to go.
2. Demand a book deal within a set amount of time. The publishing industry moves, in most cases, very slowly. It takes at LEAST a year between book deal and publication date, usually longer. And the submissions process can also be lengthy. Patience, grasshopper.
3. Talk about what a great movie your book will make. Agents are in the books business, not the movie business, and what makes a great movie might not make a great novel. It might make the transition between page and screen really well, but that's not the point at the query stage.
4. Confuse "synopsis" with "query." A query letter is about 250 words and should include a hook (an eye-catching first sentence) as well as information on the characters and most of the plot, without giving away the ending. A synopsis is usually 2-4 pages, explaining most of the scenes in more detail, including the ending. Many agencies do not ask for synopses*, whereas I've never heard of one that does not want a query letter.
5. Open your query with rhetorical questions. Here is agent Sarah La Polla's explanation on why. Essentially, if we actually answered most rhetorical questions used in queries, it would be with much more eye-rolling than you want.
*This might be because synopses are evil.