I go vertical.
Ever level has a 3x3 stair in the center. Actually the center tile is floor which eventually gets a masterwork, jewel-encrusted, gold-or-as-close-to-gold statue. So there's 8 tiles of stair around a column of statues. Surrounding the downward stairs at the surface are the depot, kennels, dump, and a armor stand for all the squads. I like my military to train full time out side so no one is vomiting during engagement. Under that is a farm layer. 6 3x5 plots tightly packed against the stairs is more than enough to
constantly have to dig for more food storage space. The next level is reserved for pasture and tree farming if the caverns get pierced. Then I dig to rock which is often the next level down (assuming there was soil at all). If rock was the next layer down I skip a layer before the workshops. Either way, I have a socks level under the farms. This is a 31 diameter circle with the manager and record keeper posted by the stairs and lots of space for finished goods and furniture stockpiles.
At this point it's about 6-10 levels of workshops. Workshop levels are circles with radius 13. Workshops surround the stairs (up to
and are grouped by utility. So the kitchen(s), still(s), butcher(s), tanner, and a farmer's shop or two are together right under the farm. Crafts are under that since many of the crafts draw from the butcher's leavings. Stockpiles are outside of the workshops.
Under this is the dining hall and hospital. They're on the same level because they have wells and it's easier to set up wells on the same level. The dining hall is large enough to seat 80 comfortably at any given time. It is semicircular and is surrounded by food storage. The hospital has soap stockpiles and lots of supplies. I find that 8-12 beds (w/tables and chests) is usually enough.
Below that are the bedrooms. I like to make sure that this level is far enough down to make noise not a problem but close enough that they're not wasting time. Lately, I give the original 7 a 4x5 room and the rest get 3x5. Once I get doors, statues, coffers, cabinets, and engravings in each room, everybody is ecstatic. I set it up so that the center of each room is no more than 10 tiles from the stairs. So the original 7 get a floor and then it's 16 per floor below that. If I were to have a larger pop cap (I'm at 80 for FPS reasons), I'd make smaller rooms and pack 20+ to a floor. But I don't usually need too many floors as happy dwarves soon double up in beds. The mayor and baron/duke get their own floor usually on the level below the wells. They're surrounded by water but don't get wet.
Once it's established and food and finished goods start getting out of hand, All the workshop levels get expanded to 31 tile circles, a live-target-archery-range is put in, and the surface gets a makeover. The surface gets a series of walls and bridges claiming more and more land w/big boneyards, pastures, above ground farms, and a separate little spot for each squad to train. I also make a little gauntlet with traps and a barracks at the bottom at the entrance to each cavern.
It's not the most efficient possible. But it's where I'm at these days.