I usually just get my seed each year from either a new packet, or an old packet that I determine has viable seed.
Also, I usually don't let volunteer vegetable seedlings stay in the ground. Usually they are plucked out as weeds.
This year, a couple tomato seedlings started growing, right next to each other, in this year's pole bean patch (which was last year's tomato patch). For whatever reason, I decided to let them grow. I had Gardener's Delight in that area last year, along with some Better Boy and a few Roma (none of which were marked as F1 seed).
They are both producing ripe tomatoes now that are a little larger than Gardener's Delight, on a shorter plant (roughly 5 feet tall). The flavor is good too. They are about 150 feet away from any other tomato I have growing.
So... is it likely to be worthwhile saving seed from these plants? Or did I just get lucky with these 2 plants, and should just enjoy them without bothering with seed-saving? I develop a blank look on my face when thinking hard about genetics... not my forte at all. I have a fruit that I am now allowing to get quite ripe on the kitchen counter. I've read up on how to process the seed to save for next year.