One of my first acts in embarkation is to plan my underground fields, and dig out rooms for them, in the copious soil I like to embark in. (Before digging out near-surface rooms/corridors, I ensure trees on the level above are felled.) My usual design means it's one (and later on, more) 5x5 room, which I may fill with 5 1x5 farm plots.
(It may initially become a stockpile (or set of them) for the wagon goods I brought, but once there's somewhere else for that I set them back up as fields and plant ASAP, concentrating on the primary food crops.)
The big trick is to ensure you don't run out of seeds. Before any kitchen gets hold of them, ensure seeds aren't usable for cooking (at least until you're overproducing them), make sure there's dedicated stockpiles for them (I make both bag and non-bag stockpiles, near the fields; the non-bag ones show 'fullness' easier) and crops rotting in the field is a bad thing (though I stick with one farmer and farmer-only harvesting in the early game for skill-training, meaning I need to sure they aren't too busy).
Raw plump-helmet eating (and getting the seeds back into all available fields promptly) can keep you ticking over if you run out of anything/everything else (at least while in season), but not fulfilling for either you or your little guys. In early trade caravans I tend to buy any and all seeds I can, mixed with a good variety of actual foodstuffs.
Aboveground, there's Herbalism/Plant Gathering and fruit-picking zones, in some embark zones, if you aren't in danger of various attackers, and I have a little trick with overground farm plots sunken into the lower layer (easier defending, gets rid if "surface rock effect" to bring surface crops into my cultivation schemes. But a good soil-layer underground set of plots is my mainstay, and so I try to plan, and eventually fill, more than enough of these to support all the underground opportunities (without having to wet any rock) and shape the rest of the fort and its undustries around that. There's always exporting, later, if I overdo it.