So we all know the following is true:
- If you screw up a query letter, then you will get a rejection.
- I got a rejection.
- Therefore I screwed up my query letter.
Even if you don't screw up your query, you can still get rejected. Why? Try one of these:
- The writing isn't "there" yet.
- The story is a subgenre that the agent doesn't really care for.
- The idea doesn't click with that particular agent.
- The idea is good, but that agent doesn't know how/where to sell it.
- The idea is too close to that of one of the agent's existing clients.
And to item #1, yes. Agents can divine writing ability from your query letter (spend a week in a slush pile and you can, too). This is the difference between "not screwing up" and being awesome. If you avoid all the major mistakes, but you're not getting any requests, tweaking the query might not help.
You might just need more experience points. Write more, critique, and get critiqued. Then come back to your query -- and your novel -- at a higher level.
Lastly, even an awesome query gets rejected. A good request rate is usually around 10-30%, for many of the reasons listed above. This is a subjective business. Get used to it (he says to himself).
Bottom line is there is no easy answer. Avoiding mistakes will not get you an agent. Writing something awesome, and finding an agent who agrees with you, will.