How do I get seeds from my basil plants?

If you have several kinds of basil or the near neighbors have a different type of basil your seeds may be cross pollinated between two types so the seeds will not breed true being hybrids. This is not always bad but the next generation of basil may be very different from the plants you have this year as a result.
Flowers have an ovary that holds the ovum (eggs). Once fertilized, seeds mature where the flower was because, though the petals drop, the ovary develops.
To reduce chances of cross pollination between basil be sure there is 50 – 100 feet between different types of basil. Or pinch one variety so the other can flower and be fertilized. Once flowering is complete allow the pinched basil to set flowers at a later time. Be sure you have left at least 6 weeks until the first frost to allow time for the seeds to mature. If an early frost catches you out cut the flower stems and put them in a glass of water iindoors to finish maturing. If the seed pods have at least started changing color, you can usually get some seeds.
Save only seeds from the individual plants that offer the best flavor and aroma. This will improve your strain as long as they have not been cross pollinated.
Blossoms on the spikes mature once fertilized and the petals drop. The green pod carpels remain and contain the seeds. These pods turn brown as the seeds mature.

To harvest seeds strip the stem of carpels into a bowl then rub the carpels to open them. Basil seeds are small, round and very nearly black. Let the seed sit to finish drying. They must be dry or they may mildew in storage. Seeds do best stored cool & dry.

Parsley sets seed the second year so if space is not limited save two or three plants to set seed.