I posted this to my blog but thought it was fitting for over here, too.
See the blog for photo inclusions as well, though. I can’t embed them all here….

http://merplants.blogspot.com/view/sidebar#!/4312246993881092744/2011/03/making-herbal-remedies.html

By growing and preserving herbs and plants, you will be carrying on a tradition that stretches back to medieval times, and earlier! One of the most important household duties of a medieval lady was the provisioning and harvesting of herbs and medicinal plants and roots. No respectable lady would be without her medicine chest, which often meant the difference between life and death. Herbs and plants were either culinary, medicinal, or for household use. Rarely were they cultivated as ornamental plants. Herbs and vegetables had to be harvested in quantity and preserved to last throughout the winter, which provided vitamins and nutrients during those months. Rosehip jelly was a favorite. Dried herbs could be left hanging or stored in jars or used in ungents and vinegars. Or they could be powdered or added to fats to create ointments and pastes.
http://www.gardeningknowhow.com/herb/the-medieval-herb-garden.htm

Just like with culinary herbs, medicinal herbs each have their own best way of use. It is recommended to consult a good guide that references the proper use for each herb before using it. For example some are injested (teas, infusions) while others are placed upon the skin externally (salves, ointments). Here’s info on how to make these.

Infusion A simple way to prepare the more delicate aerial parts of plants, especially leaves and flowers.
Place herb in strainer. Fill cup with freshly boiled water. Put strainer in cup, cover, and leave for 5-10 minutes before removing strainer. Drink hot or cold.

Decoction A more forceful way to deal with roots, barks, twigs, and berries to extract their medicinal constituents. Place herbs in saucepan. Cover with cold water and bring to boil. Simmer 20-30 minutes, until the liquid is reduced by about 1/3. Strain liquid through a sieve into a jug. Pour the required amount in a cup, the store the covered jar in a cool place.

Tincture This process encourage the plant’s active constituents to dissolve, giving a tincture a stronger reaction than an infusion or a decoction. Also they last longer, up to 2 years.
Place herb in a large, clean glass jar. Pour on the alcohol, covering the herb. Close and label the jar, and shake it well for 1-2 minutes. Store in a cool dark place for 10-14 days, shaking it every 1-2 days
Set up a wine press, and place a muslin or nylon mesh bag inside. Pour the mixture in and collect the liquid in the jug.
Slowly close the wine press, extracting the remaining liquid until no more drips appear from the pressed herbs. (Discard the leftover herbs.)
Pour your tincture into a clean dark glass jar using a funnel. Stopper with a cork or screw top and label your bottles.

Capsules & Powders Not only can you take capsules, but you can also sprinkle the contents onto food or mix with water. Apply externally to skin or mix with tinctures as a poultice.
Buy powdered herb. The finer the better grade/quality. Buy gelatin or vegetarian capsule cases from specialty outlets.
Pour powder into a saucer and slide the capsule halves together, scooping up the powder. Slide together. Store capsuled powdered.

Tonic Wines A way to prepare strengthening and tonic herbs.
Place herb in jar or vat. A good way is to use a jar with a tap at the bottom so the herbs are not disturbed.
Pour in enough wine to cover herbs completely. Close jar and shake. Let stand. Allow wine to mature for 2-6 weeks. Now you can take a dose from the jar. Regularly top off the mixture with wine.

Syrups Sweetness disguises unpalatable herbs, especially good for children; honey and unrefined sugar are effective preservatives too and provide the additional benefit of having a soothing action. A great vehicle for cough mixtures and for sore throat relief.
Pour an infusion or decoction into a pan. Add honey or sugar. Gently heat, stirring constantly until all honey or sugar has dissolved and mixture has syrupy consistency. Remove from heat and cool. Pour cooled syrup into sterilized glass jars with a funnel. Seal, store in dark place. Don’t use screw-topped bottles as they may explode – instead use cork stoppered jars.

Infused Oils Infusing in oil allows an herb’s fat soluble ingredients to be extracted. Hot infused oils are simmered. Cold infused oils are heated naturally by the sun. Both can be used externally as massage oil, or added to creams and ointments. Do not confuse with essential oil which can also be added to an infused oil to increase effectiveness.
Hot infused oils can last up to a year but are more potent fresh.
Stir chopped herb and oil together in a glass bowl over a saucepan of boiling water. Cover and simmer gently for 2-3 hours. Remove from heat and allow mixture to cool. Pour into cloth-lined jar. Pour in all liquid; press all liquid out of herb through cloth into jar. Pour infused oil into clean dark glass bottles using a funnel. Seal and label your bottles.
For cold infused
Place herb in clear glass jar. Pour in oil until it completely covers all herb. Close jar and shake. Place in a sunny spot for 2-6 weeks. Now press/pour into jar as with the hot infused above.

Ointments contain oils or fat heated with herbs. Unlike creams, contain no water. So these will stay upon the skin and form a protective layer to protect plus hold on the active medicine. Chapped lips, hemorrhoids, diaper rash.
Melt your oil or fat in a double boiler. Add the finely cut herb and simmer for 15 minutes, stirring continuously. Pour mixture through a muslin cloth secured to the rim of a jar and allow the liquid to filter through. Wearing rubber gloves, squeeze mixture to get out as much as possible. Quickly pour the ointment into jars before it sets into the jug. Jar and label the lids when cool.

Poultices a mixture of fresh, dried, or powdered herbs applied to affected area
Simmer herb for 2 minutes. Squeeze out any excess liquid. Rub some oil onto the affected area to prevent sticking and apply the herb while hot. Bandage the herb securely into place using gauze or cotton strips. Leave on for up to 3 hours, as required.

Creams Combination of an oil or fat and water, into an emulsion. If the process is rushed, the oil and water may separate. Unlike ointments, creams are cooling and soothing while allowing the skin to breathe and sweat.
Melt emulsifying wax in a glass bowl and set in double boiler. Add glycerine, water, and herb while stirring. Simmer for 3 hours. Strain mixture through a muslin cloth. Stir slowly but continuously until it cools and sets. Put into dark glass jars using a small knife or spatula. Tighten lids and label. Store in refrigerator as soon as possible as they can deteriorate quickly.

Compresses & Lotions utilize an infusion or decoction or diluted tincture; soak compress in the lotion and hold against skin. Simple way to use herbs externally. Very effective in relieving swelling, bruising, pain, soothing inflammation and headaches, and cooling fevers.

And Other preparations
Steam inhalations
Gargles & mouthwashes
Suppositories
Essential oils (the use of, not the making of)
Baths & skin washes
Cold macerations (Some herbs are destroyed when heated)
Juices

For ointment, add vitamin E to preserve.
Mix 1 part each herb and oil or lard. Add beeswax to harden.
Let herb sit in oil to absorb. Heat. Pour/strain into a jar. Squeeze oil from herbs into jar. Strain again, and again if desired, until clear. Put in pot, heat. Add beeswax. Now jar it and it will firm up.