There are two great herbs to grow in your garden: cilantro and dill.
Both of these plants have two things going for them. Both produce seeds and leaves that can be used in different applications in the kitchen. Both are also self-sowing, so they come back every year.
Let's take them one at a time. Cilantro -- the leaves are one of the bitter herbs traditionally eaten at Passover. Leaves are harvested and used in many Mexican, Mid Eastern, and Vietnamese recipes for soups, salads and stir fries. Long cooking destroys the flavor, so add them just before serving.
The seeds are called Coriander. These seeds were found in the pharaoh's tombs. Harvest them when half the seeds have turned brown. Tie harvested stems into bunches and then upside down inside a paper bag to trap falling seeds. I like to add the seeds to my pepper mill for a mild flowery note.
Dill -- You can harvest the feathery leaves as needed for in the kitchen. Added near the end of cooking to maintain its flavor, or for a garnish. I use dill in many recipes. Notably, sprinkled on deviled eggs, over grilled salmon, added to chicken soup or pasta salads before serving. Its uses are almost endless. This is the one herb that I will cut down after the season is over and bundle and dry in a cool, dry place. After it has completely dried, I place it over a paper towel and rub it in my hands to release the dill weed. I then store in a covered container in a cool and dry place for use during the winter months.
Dill Seeds -- Harvested the same way as listed above for Coriander. Both Coriander and Dill seeds; separately keep well in a covered container out of direct sunlight. The seeds are used in pickling spices and also used in breads, like Rye Bread. I like to add a 1/2 teaspoon of seeds, ground in a mortar and pestle to any meat marinades.
Note: Do not take dill in greater than culinary quantities if you are pregnant or breastfeed except under professional supervision.