An interesting set of rules I've been trying out recently:
The human town of [reallylongname] is in danger, and has made a request of their dwarven allies: Bring your legendary construction and defense skills to bear, and fortify the town against any threat.
The goal:
Build the town with a defensive system that will keep them safe long after you leave. Something that will withstand the test of time (or would, if the humans actually had the AI to use/maintain it after abandon).
The rules:
-Keep as many humans alive as possible.
-(and try to avoid using cheap tricks like locking them inside their homes)
-It's ok if a few humans die while hunting local wildlife, but if they start dying to sieges or ambushes, then you have failed.
-Don't steal human resources. This includes anything from eating their food, to demolishing the temple for raw materials. You are guests, not invaders!
-Exception 1: Maybe they will let you stay in the inn for a few weeks until you get lodging set up, if you are nice.
-Exception 2: If your plans really do require the demolition of a human structure, you have to build an equal-or-better replacement elsewhere.
-Your defenses should disrupt village life as little as possible while still being effective. Things to avoid include paving the streets with magma, disrupting people's ability to path freely amongst structures, turning the town into a charred and barren hellscape, and anything that involves blocking out the sun.
-Keep your fortress utilitarian, you aren't trying to get a king or become the mountainhome or anything, you have a job to do. Pointless luxuries are a waste of effort.
-Don't anger the other races. The town doesn't need more enemies.
Bonuses:
-Try to leave the town better off than you left it. If the only water source is a carp-infested river, build a well for them. Instead of putting your trade depot deep in the fortress, build the humans an aboveground trading hall. Maybe add some windows to the temple, that sort of thing. Leave them in your debt.