First, you always wants to use stainless steel, cast iron, or glass containers for preparation.
INFUSION- an infusion (commonly called tea) is used for the aerial parts of an herbs, this means all of the parts of the plant that are above the ground. Boil water, remove from heat, add herbs, cover tightly. Most herbs will steep for 10-20 mins.
DECOCTION- this method is used for barks and root herbs. Place herbs into boiling water, cover, simmer for 10-30 mins
POWDER/CAPSULE- use powdered herbs in a capsule, to powder an herbs use a motor and pestle, herb grinder, or purchase prepared powder. This works well for medicinal herbs with an unpleasant taste.
TINCTURE- this method works well to super-power the herb and extracts different constituents than water, so it is necessary to use this method in order to use for a specific need. Use a good reference to be sure that the herb is a good candidate for a tincture. Usually an 80 proof liquor will do the trick. Fill a glass jar half way with the herb of choice. Pour in alcohol, wait for it to sink in, add more alcohol until all herb is covered. Place a small piece of plastic wrap on top, put on lid, shake, shake, shake!
Shake twice a day for 2 weeks or longer. Keep in a dark location. Strain and use recommended dose for that herb.
TOPICAL- These methods include chest rubs, poultices, and liniments. There are many recipes that are helpful for colds, flus, muscles aches, and more.
VINEGARS-This is a type of tincture, but uses vinegar instead of alcohol. This is a great way to give herbs to your family through foods.
STEAM INHALATION/AROMATHERAPY- essential oils are used for almost anything you can think of!
SMOKING- Many herbs can be smoked medicinally, mullein for example is a decongestant and lobelia acts as a nicotine replacement.
GARGLES- This is a diluted infusion or decoction used to treat sore throats or other mouth and throat ailments.
FOOD- culinary herbs are natures magic
SYRUPS- A syrup is an herbal infusion, decoction, or tincture that you heat at a low temperature then add honey, sugar, or glycerine to sweeten.
DOUCHES/ENEMAS- usually a diluted infusion or decoction used internally
So there you have it, I'm sure there are probably more but those are the basics. Always research your herb before preparation and test for sensitivity. Have fun!