Have you read the Dresden short story The Warrior? Overtly, it's about one conflict. But at the end, Harry learns how his actions in the story had very very many far-reaching effects he completely didn't know about.
A demon could ask for seemingly-innocuous stuff that has those kinds of "hidden" knock-on effects... "Go buy that upset-looking lady at the County Fair an ice-cream cone." But what you don't know is that she's upset with her insanely-jealous boyfriend. He's walking back to her as you leave, sees that Some Other Guy has bought His Girl a sweet treat. So he drags her back home and beats her within an inch of her life.
etc...
That is absolutely an awesome idea and I will be doing stuff like that. But my problem is that I need one or two things that look completely straightforward to be the first couple of bargains. If the demon asks the wizard to buy a random girl an ice cream in exchange for valuable information, the wizard is going to go "you're a
demon, you don't do nice things, so this must be a spectacularly bad idea." Later, when the wizard trusts the demon, it won't be a problem, but the first, second, and maybe third things the demon asks for have to be the kind of thing where the wizard will go "yeah, I can see why a demon would want that, but it's not hurting any innocents, so why not?"
I know there must be things like that besides portions of a person's Name, because Harry states that he has called Chauncey up for information half a dozen times before Fool Moon, yet has only given the demon two parts of his Name, but I can't think of any.