IIIIIDEEEEEAAAAA!!!
1: embark over a vault, making sure to be somewhat for away.
2: Bring blocks from embark.
3: Bring lots of dogs, too.
4: Have one dwarf dig down into the soil.
5: The rest of the dwarves build quick fortifications around the 1X1 stair.
6: Have that dwarf do his best to survive until a migrant wave distracts the angels, then have him quickly deconstruct one fortification, run, grab a bag of plump helmet seeds, store them underground, build that fortification again. Repeat with a couple logs and a block.
7: Have him live on plump helmets and plump helmet whine.
8: Dig around in iron, getting as much iron as possible. Make armour, an axe, a shield, and some barrels.
9: Breach a cavern, but wall off a small area, preferably with a tree in it.
10: Build a wall splitting the first large room with the first set of stairs with a drawbridge. Place a lever on the inside half of the drawbridge, and make a 3X3 ramp to the surface, immediately retreating behind by pulling the lever to close the gate.
11: Build a second line, with drawbridge as well, in a similar fashion further along this room, but with walls instead of fortifications.
12: Build a trade depot in this middle area.
13: Designate the area near the ramps as a meeting area. When migrants arrive, do your best to make sure they get in, while still keeping angels out.
14: Eventually, lock the second gate, with everyone inside, allowing a lucky caravan person or two to get in, lock the front gate, open the second, then deconstruct the depot. Take the goods.
15: Survive.