1. Flowers picked to be air-dried must be as perfect as possible and moisture-free.
2. Flowers for drying shouldn't be picked too early in the day. Allow the warmth of the sun evaporate the dew first, and take out leaves from the stems to help speedy drying.
3. The faster flowers dry the better they keep their colors.
4. Collect flowers in bunches and secure the stems using rubber bands. Hang upside down on a hook in a dry, dark area.
5. Most flowers air-dry best when hung inverted.
6. Dried materials can stay hanging indefinitely, as long as they're not hanging in a moist area.
7. To store flowers after they are dry, put them between layers of tissue paper in cardboard boxes.
Read the more detailed version here: How to Dry Roses and Other Flowers