Why might my fortress not be getting migrants? I'm below the pop limit, and the game gives the "no migrants came this season". Yet I have like 4m wealth. Surely I should be getting them?
If you are not generating a lot of wealth, you won't attract many dwarves.
Some tricks I use for generating wealth rapidly and quickly.
1) Make your workshop out of the most valuable materials you can. Careful with heat-generating workshops. Making a magma forge out of combustible materials might be a bad idea.
2) Get a craftdwarf started ASAP. After my dwarves are underground, one of them starts making stone crafts immediately, and that becomes his one and only job. For a long time. Eventually they will be able to retask as a stonecarver or something, but it will take a while before they can really swamp your fortress with mugs or whatever. They will also be making pots for food storage, but don't have them do that excessively until you really need them to.
3) If you are a minimalist, and build small compact fortresses, get one of your dwarves smoothing and engraving ASAP.
4) Construct mechanisms and make traps and levers. Dwarves like traps and levers. Make these from the most expensive materials that will do the job, like workshops.
5) If you build huge open fortresses, try to limit your digging early on - mining doesn't give you much wealth, only the base value of the rock you have mined.
6) Don't atomsmash anything except refuse and really junky stuff, unless you really have to. With the new undead stuff, atomsmashing any body parts you don't use immediately would probably be a good idea.