We get so many
volunteer cherry tomato plants coming up every year that they tend to self-select for early season genetics. Whatever the first plants are that pop out of the ground are the ones that are allowed to grow. In the weeks and months that follow, we'll get hundreds more, but those tend to get pulled out and put into the
compost pile. So year after year, it's the earliest season plants that get to stay.
If you're collecting seed from hybrid tomatoes, you won't get a true-to-type plant the next season. Even heirloom tomatoes may not produce the same variety. I just buy new seeds every year. For 5 bucks, I'm sure of what I'm getting and you'll have enough seed to start a small forest of plants. The only type of tomato I don't buy seed for is cherry tomatoes because they are like weeds, popping up everywhere. I think that some of that is because the
chickens eat them and them "distribute" the seeds wherever they roam and
poop.
The way I save tomato seeds (when I do) is to simply cut the tomato in half, and bang it onto a paper towel. All the tomato goo comes out. Smear that across the paper towel and let it dry. When you go to plant, just rip the paper towel into small pieces and bury the seed & towel all together. That's the lazy method, which works just fine.
If you want clean seeds without them sticking to the towel, (like store-bought seeds) scoop the seeds and goo out of a ripe tomato and put them into a drinking glass with a cup or so of
water. Let it sit for 3 days on the counter-top until it starts to get a bit funky/fermented. Swirl the seeds around and then hold the glass under the faucet (low pressure -- just a mild trickle) and flush out the glass. The seeds will sink to the bottom while the tomato goo will flush out with the rinse water. Rinse them carefully until it's just the seeds and clean water in the glass.
Dry them on a piece of paper. The seeds come out perfectly clean and will germinate well next growing season.