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There are a number of sites that can give you a list of instructions for spells and potions in the world of Harry Potter.
This site is said to be the definitive reference in terms of Harry Potter and its spells and potions:
For potions: http://www.hp-lexicon.org/magic/potions-enc.html
For spells: http://www.hp-lexicon.org/magic/spells/spells.html