One of the best methods for getting seeds for good tasting fruits (that breed true) is to just purchase the fruit of something you like and plant the seeds inside. I do this with tomatoes all the time, just go to the market, pick up the a few pounds of heirlooms and squish out the seeds before I eat them at home. I get so many tomato starts this way, that I generally have to transplant or kill off a few.

With other plants, it's also easy and advisable just to let some go to seed instead of harvesting them. You'll have plenty for the next round.