Q. If you send a query postcard to a producer asking them whether they'd be interested in your idea, as you advocate doing in your book, and they send it back with a yes, should you have a script already written to send to them right away? Or is the whole point that you can take as long as you like on your script and then follow-up with them, even up to a year later?
In CRAFTY SCREENWRITING I advocate the unorthodox technique of querying a spec feature that you may possibly not have written yet. If no one responds, this saves you the trouble of writing a feature screenplay that no one wants to read.
I think if you take 4-6 months to write the script, you can probably just send the script "per our conversation" or "per your request." If it takes longer than that, you might have to make sure the person is still at the same company and the company is at the same address. But yeah, I think you can send the script at any point. If it was a good idea, it's still a good idea.
When you send in the email, remind them they asked for it and apologize it took so long -- you had some ideas how to improve it and you wanted to get them the best possible draft.
I'm not sure you need to use query postcards any more. Me, I'd email the query. Much cheaper. When I wrote the book wayyyyy back in 2002, fewer development execs were hep to the Interwebs. But I think everyone's got a Blackberry now.
Of course you can always just query the script after you write it. For example, if you think your hook is so brilliant you don't want to put it out there without a script attached. But if you're new to the game, or not sure how hot your hook is, then you might learn something from querying first. Heck, you could even query a bunch of different ideas to different places, to see which idea is best. This is abusing development exec's time a little, but if it results in their getting better scripts to sell to their bosses, I don't believe they'll hold it against you. Anyway, it's their job to develop. Right?