You want to avoid anything that's generically, boringly bad, since that makes for unentertaining missions. You also want to avoid anything you entirely hate. If there's a thing or two that gets your goat, that's usually fine, but you have to spend a lot of time with a text if you're going to mission it, so if you don't find its badness at all entertaining, you won't have a good time sporking it, and neither will anyone reading said spork (assuming you even finish).

You do want something that you can make a story out of—something at least one of your agents will have some strong feelings about such that comedy and a smidge of drama ensue. You should (through your agents and some good gags) be able to express what makes the writing bad, and what would have made it better.

This can be very individual, but the best way to get a sense for what tends to work (or not) is to read a bunch of other missions and see what worked (or didn't) for other people. Enabling this is why we have a wiki. {= )

~Neshomeh