When I'm not trying something interesting, I normally use the same basic layout. A 3x3x3 cube of 11x11 rooms, with floor 2 being the 'lobby'. The central column of rooms has a 3x3 stairwell leading up and down, 3 of the 'columns' are dedicated to dorms, the others are dedicated to crafting. Workshops in the basement, raw materials on the lobby, finished stuff on the top. Other rooms are attached as needed (extra storage, animal pastures, etc).
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The entryway is normally either up from the central 3x3 stairwell or a 3 wide corridor leading from one of the top center rooms, depending on how deep I go. I normally try to make the entry a 3 wide hallway with the depot adjacent and a drawbridge to button up and force invaders through a trap tunnel right next to it. Farm plots don't go in this layout, they're normally blistered as an 11x11 room above the food stockpile/kitchens, or up a few floors. I'll usually also convert the bottom floor of one of the dorms into a hospital (with a cistern beneath it for a well). Same with a magma cistern, if I find one and can be bothered to make a pump stack.
The format's really flexible and quick to designate. Sometimes I dedicate the bottom floor of the central columns into four nobles' rooms of 3x3 office and 3x3 bedroom, or other configurations as needed to keep them happy. Adding stockpiles above and below is very easy, or doing things like blistering a 3x3 room with a door for craftsdwarf workshops in case of someone demanding shells in a desert. I also tend to build megastockpiles for food and whatnot once the fortress really starts going, usually on a floor directly beneath (I'll convert the up stairways into up/down stairways).