This is rudimentary, so forgive me if I'm completely off track, but are you managing their
labor settings? If not then most of them won't do anything because they're not permitted to. (Relatedly, if you happen to use DFHack the newer versions have a built-in Dwarf-Therapist-like menu accessible by hitting the "l" key when on the units menu. If you're using niether DFHack nor Dwarf Therapist I highly recommend Dwarf Therapist to make managing labors on more than half a dozen dwarves easier.) Dwarves should come with the labors associated with their skills enabled, but since some of the profession names are generalized and therefore potentially misleading it pays to check out what the settings are.
Hunters may also not have anything interesting within reach to hunt. Farmers planting...
is more complicated than you'd think, given the number of rules involved just in determining whether the ground can be planted on or which plants will grow in your embark even before you get to the fact that you need to manage the farm plots' crop assignments for all four seasons or
the weird way the skills and labors are arranged. (I also recommend having your dwarves gather plants from outside, if the outside is safe, using the designation and the
herbalist labor. It's a decent supplement/alternative to farms, at least until you become better at farming than at defending your dwarves from basic outside critters.)