My opener is generally well-coordinated and retains the same structure throughout most any embark.
First, since this is generally dependent on my pre-embark setup:
I bring:
a lot of wood
a lot of casserite, bituminous coal, and malachite
About ten peafowl, gender does not matter
Two picks and an anvil, of course
A piece or two of cloth and thread as crude medical supplies
Small rations of food and booze (~15 food and ~30 booze)
The dwarves are:
Weapon/armorsmith
Medic/butcher (it fits well enough, and hey, gotta love the irony)
Mason/stonecrafter
Carpenter/architect
Merchant/engraver
Warrior
Warrior
1. Dig down. Normally a 2x2 staircase right next to the wagon. I'll only dig like 4-5 layers out, just enough to have a few layers of stone. Warriors will get the picks for now.
2. Dig an ~15x15 room in the topmost dirt layer (centered on the staircase), and order all wagon supplies dumped in the room. Channel a hole in the top of the room, and place a little bit of whatever is on hand to fill it back in. Make a 3x3 tavern inside the dirt room, just to make sure the dwarves stay underground and away from whatever nasties, while also socializing and forming relationships.
3. Order basic workshops (mason, carpenter, butchers (make the butcher's shop under the filled-in hole to prevent miasma), tanners, craftsdwarf, still) to be made in the dirt room, and order the first stone layer to have a ~15x15 room dug centered on the staircase into it as well. Order a 7x7 dining hall dug and eight 3x1 bedrooms to be dug, as well as a 3x3 office, all to be made in the sides of the stone ~15x15 room. Queue up six doors, eight beds, five chairs, four tables, and a few blocks for the sake of having blocks. Also, make a few mugs and set them to "do task now" or else the mason/stonecrafter will never get around to it.
4. Instead of starting farms, pre-brought animals (ie peafowl) as well as the pack animals will be butchered to provide me with early food until the first caravan arrives, in which case I will resupply and begin farming. Extra booze will be brewed from some cheap garden vegetables that were brought as well, and stored in rock pots when the mason gets done with the furniture.
5. Once the stone ~15x15 room is dug out, a wood burner, smelter, and forge will be made, and my armor/weaponsmith will begin forging bronze gear (helm, shield (cause bashing damage), mail, leggings, high boot, weapon). In the event coal cannot be brought, an even larger excess of wood (approx 90 logs) will be brought instead.
6. When the dining hall is dug (it need not be furnished) move the 3x3 tavern inside it. Also, start smoothing stuff.
7. When all mining is finished or the first migrants arrive, disable mining on the two miners, and draft them, using their military skills combined with the fresh bronze gear to jump start their training. Enable mining on the two most useless migrants when they arrive. Make a room for the barracks in whatever fashion desired: aboveground to prevent cave adaptation, off to the side like the dining hall, or just plop a weapon rack in the middle of one of the ~15x15 common areas and call it a day.
8. Start expanding rooms: dig another ~15x15 stone layer out if out of wall space for rooms or floor space for workshops, and continue to make 3x1 bedrooms until the pop cap can all have their own bedroom. Due to my favoring of small forts, enough wood is generally brought to supply beds for all of the rooms. If not, use early military to secure a small portion of the caverns and forge an axe to hack some trees down there.
9. Bronze spiked balls are made for trade if a caravan will arrive.
This opener is almost completely independent of surroundings. In hostile environments I will flaunt my excess wood reserves to make a wall around the wagon and, in the event of reanimation, make an atom smasher before butchering my animals. It sends me off with a functioning fort after only the hardcoded waves as well as a militia capable of fending off wildlife, and establishes my most prominent industries. It is also versatile in a crisis: if a dwarf or two is lost for some reason, the medic and the merchant both generally have a fair amount of free time to take over, although a distinct lack of hauling may be noticed. I will also sometimes mix and match labors a bit more even if it goes against my point assignments, things like giving the carpenter stonecrafting or masonry to mass produce pots or blocks, or giving the merchant mechanics to do whatever thing I need it for.
It will not function in only a few situations:
1. No casserite able to be brought. This is its biggest weak point, since casserite isn't super common.
2. Challenge embark with limited or no supplies. Obvious reasons, of course.
3. Aquifers. Can't dig down to the first stone layer if you have no stone above the aquifer! It functions mostly the same, but the dining hall and bedrooms will have to be moved to stone when possible, and wood may be required to circumvent the lack of stone. The 2x2 staircase happens to pair well with the double slit method, though.
4. Some mods can drastically change the nature of it. However, with some adaptation, it functions with most mods, and in fact, it works even better with masterwork: bronze can be cold forged and plump helmet men can provide food and booze right off the bat, both of which are major features of the embark.