If I dig into the side of a hill or cliff, I need at least four layers above the entrance to be in line with it, like a sheer cliff, and I'll spend a lot of time channeling or building walls until they are. I also remove all the ramps around the entrance because I don't like the idea of enemies coming from directions that aren't line-of-sight from the door.
On the other hand I have no problem with starting a fort straight down rather than into a hill. I tend to prefer rather extensive above-ground farms, palisades, towers, and roads. I like to make it look like an actual settlement when viewed from outside, rather than just a door or hatch into the earth. Otherwise the filthy elves might get the idea that the area is uninhabited, and try to get friendly with my timber.
Almost always, my halls will be 3 tiles wide, and will terminate in a 2x2 stair complex. Lately, rather than putting workshops into rooms off of the hallway, I'll just widen the hallway by 3x3 or 3x4 where I want the workshop to go. Who cares if a Dwarven hallway is noisy? The sound of the forge is soothing.
I almost never use ramps underground, though if I embark in an area that has a plateau/valley situation, I'll ramp a tunnel to connect them with roads coming out either end, and build my fort around the tunnel, with the main entrance in the center of the tunnel. Makes a great choke point, and it's kind of like a toll booth.