I don't like mountains. When there is a mountain or even just a hill, I get rid of it no matter the cost. (No military for 2 years? No problem. Got miners with picks that can fetch arrows out of the air with just that. They'll prolly lose a limb or two fighting off goblins, but hey - we got the best doctors one can have. Dabbling ... ... oh gawd.)
I don't build a dining hall. I'll eventually do, just to complete the fortress, but no one will ever use it. Neither as a meeting point, to eat, nor will someone ever trespass except for hauling or mining. The living quarters for the average dwarf in my fortress are royal bedroom. (Thank the engraver.)
I don't like a direct entrance to the caves. The digsite to get metals, entrance to magma and the caves, is always outside of the inner fortress walls, with a seperate living quarter, food stockpile and its own useless military without equipment.
My dwarves like to live outside, letting it rain on them and standing outside in snowstorms. If they don't, they better get used to it.
My dwarfs like pets and war animals. I don't. Except grizzlies, giant eagles and lions. Everything else will eventually end up at the tradepost as totems, decorated crafts or bolts. Two cats are okay tho. Since they decided to graze my freaking grass, I have even more reasons to slaughter them all.
I don't use working burrows. Except I go into bloodrage of my carpenter farming and dropping the plant on the ground because there are no barrels to store it into. (Goddammit!)
I never fight humans or elves and always follow the tree limit. Just because I like to trade. Tho I fully support any hate on elves.
I don't use third party tools to manage my dwarfs.
I've never used a single cage trap in my fortresses so far. And only one hunter. I hunt with military and weapon traps. Or miners as military, because there is a mountain in the way.
Steel is just good enough for my military. If there is just copper, iron and bronze or worse: leather, bone or wood, they rather fight naked and die in the process. All of them. And the civilians as well.
I always meet my nobles mandates and never kill them. Even that slade loving bastard with his slade item requests. Damn him - he imprisoned up to 5 people at the same time. That's why my prison cells are never below masterfully decorated rose gold chains. Gotta make it comfortable for those legendary guys and gals.
My hospital(s) is (are) always able to house at least 3/4 of my fortress. Even with 200 dwarfs. And those rooms are as comfortable as the rest of the engraved fortress. Just a bed and traction bench does not cut it. They got no TV, so they need engravings to read, statues to fathom and masterfully worked chests to look at.
When I'm losing and going to abandon my fortress, I genozide my enemy with Runesmith just to prove my point. At least with my games I want to have the last word.