Forget buying tomato plants at the nursery. Instead, grow tomatoes from the seeds you save.
1. Choose the tomatoes carefully.
Use open-pollinated varieties or heirlooms instead of hybrids -- their seeds will bear fruit similar to that of the parent plant. You can save seeds from a hybrid, but the resulting plants might be different. Find tomato varieties from other gardeners who save seeds, Internet trading forums or specialized seed companies.
"Take the seeds from the most delicious plant," says Joseph Tychonievich, author of Plant Breeding for the Home Gardener and creator of the Lynne Rossetto Kasper tomato. "Of all the ones you have, whichever has the best fruit, that's the one you want to save seeds from because that is going to give you the best babies."
Select the best fruit from that plant -- skip tomatoes that are over- or underripe or misshapen.
2. Deslime the seeds.
Cut the tomato in half widthwise. Tychonievich says: "Squirt out the seeds that are suspended in slime. Put that in a cup of water and let that sit in water at room temperature for 3-4 days. It will start to ferment, which will actually break down that slime."
The slime that Tychonievich mentions inhibits germination. As the mixture ferments and the slime breaks down, the seeds will sink to the bottom and mold may form on the top.