I'm not the best fall gardener, but I get by. Seems like every August, I come across a stash of greens and roots packets that are years out of date, and, rather than try to do anything meticulous like sort by year, look up the viability date range, and do a germination test, I wind up funneling the lot into an empty seasoning shaker, stir them a bit, and head out to the bare spots in the garden with Darwin on my mind. The procedure involves clearing a patch in the mulch with the ho-mi (basically a right-angled trowel), testing the ground a bit (the beds harden up some over the summer), doing a little clod-busting as needed, shaking some seeds out over the "hill," and throwing some prepared soil (stolen from molehills) over them. I'm chintzy with the planting soil, so this method tends to favor the lettuce seeds over the others, which is fine by me.
Invariably, on these expeditions, I come across scads of volunteer potatoes and onions and such. I pocket them, take them in (it's approaching 90F out there anyway), give them a washing up, and carry them over to the chopping block to work up a fresh lunch.