Drying

If you have the space, drying is the simplest way to preserve herbs, seeds and flowers. There are several ways to do this:
 

Herbs can be snipped at the base of the plant and hung upside down, out of the sun. When the plant is dry, break off the leaves and crumble them to the desired texture;

For smaller plants, they can be hung inside paper bags to avoid attracting insects such as fruit flies.

Larger plants can be wrapped in cheesecloth or muslin for protection from dust and insects.

Herbs can also be dried, either in bags or cloth, in the freezer. This will help with the color retention, which is beneficial for culinary herbs such as chives, basil and parsley. It is also the only way that I know to keep any flavour when you dry chervil.

Herbs are normally hung from the ceiling in my house because I have six cats. In a house without pets or small children, herbs could be hung from wooden clothes dryers.

If you are saving your flower seeds, the mature flower heads should be picked after they bloom but before they "fall apart". Pick the flower heads in the afternoon, when the dew is completely dry. Store them in paper bags (makes them easy to label) until spring. I store the bags in ventilated bins.

Wherever you choose to hang your herbs and flowers, the temperature should be fairly constant to minimize bacteria growth from moisture.

To seal or not to seal....
Vacuum sealers are very useful to have when you are preserving food. Once my herbs are dried, I crumble them into smaller packages, which I seal and pack away out of the light. Herbs will last perfectly well in jars stored in a cool dry place, if you don't have a sealer. Why I like the sealer is it allows me to keep the herbs longer. Why is that important? Then I don't have to grow each annual herb every year. The other advantage to having a sealer is that you can break down packages of seed into smaller lots. Most home gardeners do not need to grow a full package of seed and this ensures that the leftovers are kept fresh for the next year. Of course seed collected from the garden can also be kept longer this way.

Saving Seeds..
This is so much more than saving money. Gardeners' Wheel explains how every garden has its own little microclimate. Every year that you save annual herb, vegetable and flower seeds from your own yard will give you another generation of plant that is more suited to your garden's own ecosystem. As seed companies introduce new hybrids, old favourites can become unavailable unless you have saved your own seed. As well, every generation of saved seed will become more resistant to the diseases in your own area. Gardening can be an expensive hobby and many groups have seed and plant swaps to keep things affordable.

Please Note: Not all seeds save equally well. Seed that are large enough to be attractive to birds and small animals will be difficult to save. In my yard, before the nasturtium blooms have matured the seeds are gone. I consider that the benefits of encouraging wildlife in my garden far outweigh small losses like that.