I seldom save seeds from our vegetables. Exceptions are:
Of course, the seeds I do collect are from open-pollinated varieties.
I save seeds for only one variety of tomato. It is not commercially available, as far as I know. The main reason is that this variety, TPS Golden tomato, mentioned elsewhere, has shown unusual resistance to late season blight. It's a plus that this golden is a beautiful tomato (by shape and coloring) and it has most appealing flavors.
I am selecting first for blight resistance, so I collect seeds from tomatoes on plants that have not been affected by blight and whose fruit has not been tainted. Other characteristics seem common to all the fruit, except I avoid collecting from the smallest tomatoes.
Except in the hoop house I have isolated TPS Golden from other varieties to avoid possible cross-pollination. In the future I will scrupulously isolate the Goldens.
I use a method generally recommended by master gardeners, fermenting the seeds to separate them from the gel. This:
Here's the procedure:
To separate the seeds:
I leave the seeds to air dry for a couple of weeks. Then I put them into a paper envelope and store in a cool, dry, well ventilated place.
I don't generally save seeds because:
Some of the above are reasons why I don't take locally saved seeds at a seed exchange. (I still remember the "turnip seeds" that were a really a mixture a radish and who knows what!)