Obtaining ingredients
Most ingredients can be harvested from plants all over the world or purchased from fellow alchemists, but there are some that are only dropped from certain enemies.

Ingredient Effects
Each ingredient has four effects and the higher your alchemy skill, the more effects you have available to use in potion-making. For a full list of all ingredients and their effects and location, you can download this Excel spreadsheet, or view it as an html page. One effect is revealed at each skill level. Until you see an effect listed on an ingredient in your inventory, that effect isn't available to you.

Making Potions and Poisons
You make potions by mixing ingredients with the same effect. When you have two ingredients with the same effect, your potion gains that effect. Potions can multiple effects too. For a list of some known recipes, click here.

Apparatus
Even if you have the correct ingredients, you need the right tools to make potions. First off, you'll need a mortar and pestle. The quality of your mortar and pestle affects the base potency of your potions and poisons. Also useful, but not required are: A retort, which improves the positive effects of a potion, an alembic, which reduces ay negative effects on a potion, and a calcinator, which increases the potency of all of the potions effects.