Fortunately there are many flowers that dry well; so experiment with flowers that you like. Do not harvest growing plants until they are completely dry of any rain or dew. Pick them at the base of the stem for long lengths in arranging. Place cut flowers in a warm, dry area away from direct light. The simplist method of drying is air drying where the plants are hung from a wire to dry naturally.
Drying time varies considerably depending on air temperature and humidity. Once the drying is complete you should store them in a place that won't require you to move them around frequently as they are delicate. Never store them in plastic containers or plastic bags as they will sweat and then rot. Keep them in a cardboard box with ventilation holes. If the flowers were preserved using silica gel, apply a thin layer of the gel to the bottom of the box.
Methods of Drying
For bulk drying large quantities air drying is the best method. Strip off unwanted leaves. Bunch the flowers together using an elastic band. Don't bunch too many together or allow the flower heads to closely touch each other. Some very large heads are best dried individually. If you tangle leaves and blooms together in the bunch they will stay in that position when dried. Hang them suspended from secure hooks in a place with air circulation. Drying time is anywhere from a few days to several weeks. You can tell they are ready when they feel quite crisp. Easy enough!
A very different process to get dried flowers involves using silica gel. It results in the flowers retaining spectacular color and appearing almost fresh. The silica gel (resembling rock salt) must be ground to fine granules. It can be reused countless times. This method works for flower heads. Once the flower head is totally dry you can begin. Egg cartons or small plastic flower pots are ideal as the holding area for the gel and flower head.
Tins can be used for a large quantity of flowers. The egg carton or pot must be filled 1/3 full of gel. Set in the flower head and start with the outer petals and work in. Gently spoon the gel between each petal. Do this until the head is fully covered. Cover and check on them in 2 days. Remove flower heads when dry to avoid overdrying them. Large-headed flowers sometimes take 5 days. Be extremely gentle in removing the flower. Excess gel can be removed with a fine watercolor brush. To revive the flower's color spray a bit of wax polish on it.
A suitable method for drying large flowers like sunflowers and peonies is to dry them flat. Lay them on a wire garden sieve and rest it on raised objects to create a space. Again, drying time can be 2 to 5 days. Another method for drying in emergencies uses an oven or microwave. The trick is to set the temperature in a conventional oven at its very lowest setting. Drying will take 30 to 60 minutes. A microwave oven should be set very low. Check the plants very frequently. Try once each couple of minutes.
Glycerin is the perfect substance for preserving plants such as mimosa and gypsophila. Boil about 2 pints of water and add a large tablespoon of salt to dissolve in the water. After the water cools a little pour into a jar. Stand this jar in a bucket as support for the plant. Stand the stems in the hot water for 24 hours. Make a mixture of 1 part glycerin to 2 parts hot water.
Replace the old water with this new mixture and stand the plant in it up to 10 days. The leaves will look darker and feel slightly sticky when ready. During recent years dried floral arrangements have become popular and much loved. You can arrange your flowers in a container of your choosing. You could press flowers with a flower press instead of using previous drying methods explained in order to display your flowers flat.