Pick and cut flowers
Pick and cut your flowers when they are as dry as possible. This generally means you should pick them on a dry day, in the late afternoon - never pick flowers in the morning or after it's rained.
Strip the foliage from the stems of your flowers before you begin to dry them.
Technique #1: Dry flowers upside down
Many types of plants will dry beautifully if you hang them upside down in a warm place for a few weeks. This technique works best for drying grasses and seed-heads. Also lavender and hydrangea dry well with this way.
Make small bundles of three to four stems and use a rubber band to fasten them together near the bottom of the stems.
Hang upside down
Hang your bundles of flowers upside down in a dry, well ventilated place that is out of the sun. An attic is a perfect place. The flowers will be dry in two to three weeks.
Technique # 2: Silica Gel
If you feel it's important to retain the flowers' full color and form, you should dry them in Silica Gel. This fine, sand-like material absorbs moisture and supports your flowers as they dry. This is especially important for three dimensional flowers such as roses. [Used alone, this technique will dry your flowers in two to three days. Here we will speed things up using a microwave.]
Pour silica gel in a microwave safe container
Pour about an inch of silica gel into a shallow, microwave container.
Trim off all but about a quarter inch of each flower stem.
Place flowers in silica gel
Place flowers face-up in the gel.
Cover flowers in gel
Cover flowers in silica gel until they are completely covered. Be careful not to disrupt petals as you pour in gel.
Microwave the container
The timing and heat level requires some trial and error because each flower is different. To start out, use the defrost setting. Run for one or two minutes and stop to check progress. Try not to overheat as the petals will get overly brittle.
Tip the container to the side so the silica gel crystals slide away. Gentle lift the flowers from underneath, taking care not to disturb the dried petals.
Brush the petals
Use a fine brush to gently brush away any remaining grains of the gel.
Spray with sealer
To keep the flowers from re-absorbing moisture, you can spray them with an acrylic sealer.