There are several different methods of saving tomato seeds from one year to the next, some of which involve plastic wrap, boiling water, mold and / or fermentation. The rationale behind these somewhat complicated methods is to sterilize the seeds to kill any diseases they might be harboring. Good stuff, to be certain, but for years, I've had success without them.
This year's Great Long Island Tomato Challenge winner, John Salvador of Port Jefferson Station, favors a simpler method as well. He's been growing giant Bull's Heart tomatoes from saved seeds for nearly 20 years, so it's safe to call this method "tried and true."