Sterilize a glass bottle or jar with a tight fitting lid. I filled mine with water and heated it in the microwave until it boiled. Rinse the tarragon and put several sprigs into the jar. You can break up or bruise the herbs if you want to in order to bring out more of the flavor, but I just left mine as is. Fill the jar with any plain vinegar you like. I used cider vinegar because I love the flavor. Make sure you completely submerse the herbs. Cap or cork your bottle and set in a cool dry place for a couple of weeks. The flavor will get stronger the longer it sits. When the flavor is as you like it, pull out the tarragon.