In my childhood memories, certain people shared the wonder of seeds. My grandmother Anna 
handed me a round pod from a tall hollyhock, opening it to display the way the seeds were all nestled in a ring, telling me that we needed to plant them in late summer to grow and flower the next year. I promptly tried to plant them under an Ailanthus tree, and learned that hollyhocks need sun.
When I was in elementary school, we students were given boxes of seed packets, and after being pumped up by classroom speeches, were sent home to sell them door-to-door, thus improving the world and gaining fabulous prizes. I can’t remember if it was a result of one of these campaigns, but my mother planted a package of Four O’Clocks near the SW corner of our house. The little things that looked like pebbles became a temporary shrub, “The Marvel of Peru”, that was covered in flowers by the time school began in fall.
My dad occasionally planted a row or two of peas, and the vines produced pods that we could pop open, eating the delicious raw peas. Maybe my father had hoped to grow real crops on our acre of suburban prairie? After all, our neighbors treated their acre like a miniature farm, with a vegetable garden, dwarf fruit trees, goats and grapevines. That was possible for two mature people – but our well could barely meet the household needs of a family with 5 kids. There was enough surplus water left for keeping saplings alive and growing a few vegetables, but no mini-farm for us.
I was not yet out of my teens when I married Philo, and discovered that my husband was a born gardener! Even when we were newlyweds, living in beat-up grad student housing, he planted sunflowers, radishes, peas, and marigolds in the tiny patch of land around the house. Another graduate wife gave me a few divisions of perennials – oxalis, chrysanthemums and iris, and our plant propagation pattern began.
We had space for medium-size vegetable gardens in each of our three Illinois yards, always with tomatoes, peppers, and of course peas in the vegetable garden, and with summer annuals like zinnias and marigolds in flowerbeds. 
By the time we moved to our second house, the Sugar Snap Peas were introduced, just in time for the stirfry craze to sweep the country. We experimented with other interesting vegetables from the catalogs, like delicious Kuta squashes, the new Gypsy peppers, and the very odd Asparagus peas, and we began growing fresh herbs like basil and dill. Some things were planted directly but some were started inside.
When the catalogs came, we’d look them over for weeks, finally making our decisions. Since many favorite vegetables and flowers were available at local stores like Franks, we concentrated our mail orders on the ‘special’ seeds. At that second house, I still scattered cosmos and alyssum, marigolds and zinnias, but my heart belonged to iris, clematis, peonies, lilacs, phlox and other perennials that were shared by division, rather than seed.
When we moved to house # 3, there was a somewhat larger space for a vegetable garden, and there was basement space for seed starting.
Philo built a 4’ X 2’ wooden box, with 4-inch sides, and set it on a worktable so it was at waist level. He cut a section of ½ inch hardware cloth to fit the box exactly, then wound silicone-coated heating tape back and forth, so that all parts of the box would get even heat, making sure the end of the tape with the plug hung out of the box at a corner. He’d scrounged some old wooden window blinds, and took them apart, cutting and fitting them to make a grid, which divided the box into planting squares. This framework was filled with a light potting soil – not the store-bought kind, but a mixture that he’d stirred up like an alchemist in his wheelbarrow. Now it was time to plant the seeds, with the name of each variety written on the wooden wall of each square. Once the seedlings broke ground the lights were turned on. The light fixtures were also scrounged, the old fluorescent tubes replaced with grow lights, and the lights were hung on a frame made of PVC pipe. Philo designed the frame so it could be disassembled and stored.
With this system, Philo grew interesting, hard-to-find varieties of tomatoes and peppers, and I was able to start perennials from seed, like Blackberry lilies, columbine, white coneflowers, Lychnis coronaria alba and splashy hardy Hibiscus.
Those twelve years at house & garden # 3 were the high point of our seed era, ending in 1999 when we came to Texas. We still garden here, but it’s a different kind of gardening – 
at the last house, the vegetables had to be protected from the deer and grown in a 5' X 12' wire enclosure!
Now in house # 5 we have a small garden area, but with no basement or attic, where could we even set up the seed box? Luckily for us, the Sunshine Community Gardens here in Austin have a sale of plant starts and plant divisions every spring. The lines are long, but Philo has been able to try all sorts of tomatoes and peppers, including heirlooms.
I’ll answer a few of Carol’s questions:
Buy seeds? Yes, we still buy some seeds, but also buy a lot of starter plants. When I am in a nursery, a big box store, gift shops belonging to parks, or even in unlikely places like the dollar stores, I’ll run my eye over the seed racks. To a casual observer, my purchases might look like impulse buying, but I keep a sort of mental wishlist, so if I see the ones I want, I grab them, wherever they show up. That’s why I have a package of heirloom 'Cupani' Sweet peas ready to plant – they turned up at Red Barn and I grabbed them.
Seed Catalogs? I’m ashamed to admit this, but since moving to Texas in 1999, we’ve become such crummy mail order customers that no one even SENDS us any catalogs! I do browse the Park Seed site, but the Plant Delights site gets more hits from my computer.
Bulk seed store? One place we frequented was Pioneer Feed and Grain back in Illinois. It’s a cool old-fashioned place, with some seeds by the scoop, as well as seed potatoes and onion sets.
Save seeds? I save the seeds from many plants, like Moonvine, Blue Pea Vine and Hyacinth Bean. I buy basil seed, alyssum, and sometimes zinnias for cutting. There are always a few seed packages in a basket in the breakfast room.
Since we moved to house # 5 in this warmer climate, some of our annuals and perennials feel quite at home here, and they volunteer all over the place. Sometimes the 'Coral Nymph' salvias, Cardinal vines, Larkspurs, Verbena bonariensis, marigolds, Cooper lilies, Purple coneflowers, Balloon flowers, Cupheas, Sunflowers, ‘Katy’ Ruellia, Pavonia/Rock roses, and cilantro choose a different place from what I had originally planned. If that place is a better choice, they can stay. If I don’t approve, they’re weeded out or relocated.
As the garden evolves, it seems less necessary to plant seeds – and more important to recognize seedlings.
A few hours later the sun had warmed the patio so I buzzed out to look at the camellia - the open flowers were frozen, but there's a good chance the buds will be okay. I counted at least 2 dozen buds still unopened. The flowers look interesting - like faded fabric flowers pinned onto a real shrub. 
As I passed the patio table I got the idea to first pull off some yellowed or black-spotted leaves, clip off dead twigs and remove dried tree leaves from the surface of the soil. 
With dozens of seedlings popping up in every border we're not likely to run out of 'Coral Nymph', so the Cape Cod weeder is fetched to tease this one out before it overshadows the intended inhabitant. 
I also notice Philo examining the array of tools and looking out at the plant nursery. He has "that look" - and I know we'll be back for another visit.