Generally, I like digging straight down into a flat plain, with a brook nearby.
In the first soil layer, I lay out a pair of huge rooms flanking a 4-wide corridor, with stairs up at one end and down at the other. This corridor goes down until I stop mining out Z-levels for the main use.
One huge room is the workshops, the other the main stockpiles. The first rock layer is for the bedrooms, with noble quarters below.
After a while, I build a curtain wall around my original staircase, and add a secure main entrance to the fort and trade depot.
After that, I set up an aqueduct from the brook, and drive wells into it for a water source for the medics. Two farms underground, one above ground, and an archery platform over the main entrance, and all I need to venture outside for is wood and stashing goblin crap.
The legendary dining room is designated anywhere made of valuable minerals, and is engraved and has an artifact stuffed in there somewhere.
Other artifacts are used for instant room value increases.
My current fort has two soil levels, however, and so the lower one contains the barracks, the trade depot, and vast stockpiles.
The legendary dining room is in the first vein I found; malachite with a few gem seams through it. It's got a malachite coffer as the central artifact, and is dominated by the primary booze and food stockpile.