1. Make sure I'm bringing enough food/booze. My latest fort has gone 4 years (47 dwarves currently) without planting a single crop or hunting a single animal. I've survived completely on trading.
2. Designate almost my entire fort. My current fort has a 5 by 30 by 3z entry hall leading to a 30 by 60 by 5z dining hall, flanked by two 2z tall future merchant areas and the kings throne room. Above the merchant areas are 2z high throne rooms, offices, and a barracks near an armory, shooting range, pump gym, and entry fortifications. The entire fort is linked by 4, 3 by 3 stair cases, 30 apart. Below the hall is a food storage floor, then a farming floor, main storage floor, workshop floor, magma floor, magma drain floor, and obsidian mine floor. 3 floors down are 4 floors for housing, designed in a 16 gear shaped fractal pattern around the 4 stair cases, capable of housing 384 single dwarves (more if married). Below that are two double z high large gear shaped large housing areas capable of housing 40 nobles, founders, and legendary dwarves. Below that are two floors devoted to the king's bed and dining rooms. Finally the last two floors make up the tomb, shaped into a huge hammer, built for expandability and capable of holding literally thousands of dwarves while still keeping the same shape. Needless to say, I spent an entire day designing this thing (being unemployed and between college semesters helps)
3. Dig out the entry hall and build an airlock defense. Easily the most effective defense and the easiest to build. Your dwarves are cut off from the outside world, but traders can still reach you. The only vulnerable moments are when immigrants and trade liaisons need to get in, or when you need to chop wood. In those cases, I have 15 stone fall traps built outside the entrance. Chop down about 500 trees, build 5 beds for my starting 7, and start churning out rock crafts.
4. Finish digging the dining hall, barracks, and food storage floor. By now I should have had my first big wave of migrants who help me dump all of the stone in the storage floor (I'm not a fan of soil forts and like building into cliff faces). Cross train everyone in wrestling. Move 500 logs indoors.
That's about it for my first year/year and a half.
5. Dig out the other industry floors, dump the farming floor stones, find the underground river/lake and magma pipe.
6. Muddy the farming floor, set up farms. Build an aqueduct to power 3 pumps at a "magma pipe sweet spot" tm. Build multiple, redundant drains and floodgates for the magma. Pump the magma below the workshop floor (if you do this right, it will flow across a map faster than water).
7. Build farming industries. Build armor and weapons and train up a proper military. Dig out housing areas and tomb and move civilians out of the barracks. This is where I am now.
8. Grow population, get nobles and king. Set up all industries. Put doors in all entries, coffins in all tomb spots, and furniture in all rooms. Smooth and engrave all walls/floors and remove scaffolding.
9. Decorate everything. Search for HFS and begin mega project: sealed temple. Turn adamantine into nifty items.
10. Think of a new mega project and/or enact dwarven apocalypse.