Store each kind of dried material in separate containers. Glass jars with tight lids are a good choice. Check the jars after two or three days. If any moisture is visible, remove the lid and dry more. When it is time to make the potpourri, you will need to decide on a fixative as well as which oils you will use to make a great smelling potpourri.
Some good fixatives are orris root, calamus root, oakmoss and tonka bean.
Whole or crushed spices like allspice, cinnamon sticks and cloves may also be added. The material you have gathered may not have enough fragrance on it's own, or you may want a different scent. By blending different oils with the plant material you can have just about any fragrance you desire. Always use top quality oils and other ingredients. Your potpourri will not only smell better, but will hold its scent much longer.