Potions are not necessarily a form of magic; however, they can be charged with a specific purpose while you are making them. A potion can also be called a tea, a tincture, or a brew. Teas are made by steeping herbs in hot water, as are brews. Tinctures are made by slow soaking of herbs in an alcohol base such as vodka.
If you are interested in making your own teas I would suggest the following books:
"The Complete Book of Incense, Oils and Brews" by Scott Cunningham
"Magical Herbalism" by Scott Cunningham
"Herb Magic for Beginners" by Thea Sabin
And always remember that some herbs are poisonous so always be sure to read thoroughly about any herb you are considering ingesting before you decide to put it in your mouth. If you find a book on herbs that does not contain warnings of what herbs are safe and what are not, then it isn't a good book to be working with.