The Art of Drying your own Product
Preserving the life and beauty of your floral materials for as long as possible provides great longevity and sustainability. Drying any leftover flowers and greenery from an event that can be reused for another project is a great way of giving a new life and style to your previous product.
Method one: Air Drying
The best products to air dry are that which already have a hardier more wood like stem and hold less water. The reasoning for this is because often times flowers that hold a lot of water will rot before they can even have time to dry. For the best results turn to flowers like roses, larkspur, hydrangeas, lavender, marigold, thistles, strawflower, and filler flowers like baby's breath, astilbe, amaranthus, and queen anne's lace.
In terms of process, this is a very easy and inexpensive route to go. The important key tips are to make sure your flowers are clean and you've removed any excess leaves off the stem. Then tie your blooms in a bunch and hang them upside down in a space with good airflow. In order to maintain a bit more brilliance, keep them in a darker area. The flowers should hang for a couple weeks and when you are able to cleanly snap the stem your flowers are completely dry.

In terms of results you can expect something very similar to the photo below. This method will produce a very antique styled dry flower with a sepia tint that is perfect for any project with a more muted neutral or bohemian feel.
Method two: Drying with Sand, Cat litter, or Silica Gel
This method is more involved, but it does leave you with a more vibrant preserved looking product. You can use these products on any type of flower that you like as long as you have enough materials and space to fully cover your blooms in the gel, sand, or litter. Some favorites are pansies, peonies, daisies, carnations, zinnias, sunflowers, and bachelor buttons.
Though the steps are basically the same, the litter and sand do take longer and do produce a less reliable and consistent result. Regardless, for all three you will need to trim your flower so that the entire stem fits in your container with 1-2 inches of additional space at the top. You will then cover your blooms fully with the dry ingredient and let sit. You can expect your gelled flowers to be dry in 3-5 days, while the sand and litter require more like 10-20 days.

The results you can expect are more vibrant flowers retaining the look of a freshly picked bloom as opposed to the air drying method. It is recommended that you seal these blooms in order to maintain this vibrant state though.
Note:
Because of the nature of silica gel, it is important to use proper protection when working with it and be aware to not use those flowers in way that could be ingested.
Method three: Dehydrating
The last method we are gonna briefly cover is dehydrating your flowers. You can use any kind of flower with this method, however you will need a food dehydrator. Small pom-like blooms do best as they tend to fit well and not become brittle, for example zinnias and marigolds are lovely.
Depending on the size is will take 1-3 hours, with periodical checking to get the perfect dehydration. this method is fairly easy without a lot of mess or tedious steps, especially if you already own a food dehydrator. Moreover, if you are looking for a safe option for making potpourri or just petals this is a great go to.

Result-wise you can expect these blooms to change a bit in color. Pink and purple hues will deepen in richness, while your yellows will hold quite true to their fresh state. The only warning for this method is to be aware that over drying will cause a brittle affect and can lead to crumbling.
Overall, regardless of the chosen method, drying your flowers and greenery is a beautiful way of preserving and even giving new life to flowers. It keeps their sentimentality present and promotes for a very sustainable option of reuse.