The Snarky Gardener shows you how to save tomato seeds using a 5 step process
1. Let the tomatoes ripen.
2. Cut open the tomato and scoop out the seeds
3. Put the seeds into a covered glass or jar. Add water.
4. Let sit for 3 days or so, stirring once a day
5. Strain seeds from the liquid and put onto a plate to let dry for a few days.