I've just finished putting together a video on how to make mission series that are suitable for tourists to your town - mission series that will not be too hard, even for an agent who's never walked your streets before.
Good video, hilarious with the evil version of yourself lol
I'll add one more thing to the evil side: Making the mission set backwards!
See example. You start at the end and finish at the beginning, each mission you do, you have to backtrack to the other end and start from there. It's terrible! Something that should only take 10-30 minutes to complete takes a few hours instead. It looks like that mission has since been fixed up actually, but it was a pain to do it originally, the creator didn't even bother completing it themselves lol