Updated Sun, Apr 27, 2014 by skylatron
Provisioning is the crafting of buffing food and beverages. The crafting menu is a lot simpler than the gear-crafting menus - you make either food or beverage.
1. Gather Resources
You know all those barrels, crates, sacks, baskets and urns you see everywhere? That's mostly all Provisioning ingredients. You'll get tons if you loot everything you see.
Unfortunately, this can also lead to extreme inventory bloat, and all of the Provisioning ingredients are 0-value items and you won't be able to use them all unless and until you find all the proper recipes.
2. Acquire Recipes
Back in beta, looting all the urns and chests and crates in Coldharbor yielded oodles of Provisioning recipes. I usually came out with all of the beginner racial recipes - one of each food type for Health, Stamina and Magicka buffs. This is no longer the case, though - Provisioner recipes are green loot drops, and they rarely ever drop in Coldharbor anymore.
You can only prepare foods for which you have the recipes, so if you want the full array of buffs, check the auction house for them, or watch general chat for players selling them.
3. Start Cooking
Straightforward - find a cooking fire, pick the recipe for which you have all the ingredients, cook it up.
Potion brewing is a little more complex, because the ingredients are more rare and they have multiple effects.
Each brewing reagent - flowers, mushrooms, roots, leaves and such - has 4 different properties, and must be combined with other reagents with the same properties in order to make a functional potion. If the selected reagents have two shared properties, the potion created with them will have two effects. This can be awesome (for example, if a potion has both Restore Health and Restore Stamina effects) or it can be kind of useless (for example, Restore Stamina + Drain Magicka). Potions with negative effects are used as poisons, unless they are mixed with beneficial effects, in which case they are consumed as normal potions.
1. Gather Resources
Alchemy resources show up everywhere. If you see a brightly-colored plant that slightly stands out against its surroundings, chances are that it's an Alchemy reagent. Some plants are more difficult to spot than others - Luminous Roussala, for example, I only ever find by accident, but some are low-lying plants often obscured from sight by tall grass, or the colors don't stand out as strongly against the environment.
I find that there's not nearly as much competition for these resources as there is for any other kind. It may be because the plants are occasionally difficult to spot and are easily passed-by, but I find them growing fairly frequently even in very heavy-traffic areas. Your mileage may vary. They're still fairly rare anyway because of the wide variety of plants - you might come up with a good armful of Alchemy reagents, but they're all different items.
You'll also need to collect water for brewing. This can be found in wineskins or in little steamy, bubbly patches in rivers and other natural bodies of water. The type of harvest water determines the strength of the potion - for example, the "Natural Water" that you find in Coldharbor urns and such will make level 3 potions, but "Clear Water" found later in the game is used to make stronger, level 10 potions.
1a. Discover Basic Properties
All Alchemy ingredients have four properties for brewing, but when first discovered, none of these properties are known. You can do some experimental brewing to unlock these mystery properties, but there's always a chance you will combine two completely incompatible items and fail to unlock the properties of either.
There's one guaranteed way to unlock the first property: eat the plant. Use it like a potion or food, and you will unlock the first, main property and receive that effect for a short time. This can be helpful if the plant has a Restore property, or not so great if it has a Ravage property. Obviously, this is an in-game-only thing - in the real world, this kind of testing is liable to get a person killed, so don't try this at home, kids!
Add your water to the brewing stand and start mixing and matching your herbs. You will need to do a lot of experimenting to unlock all the hidden properties of the reagents, and you will probably end up wasting a lot of reagents doing this.
If you want to avoid waste, just combine ingredients that have the same known properties, which you gleaned from eating them. But if you don't mind the cost of experimentation, go ahead and try out lots of weird combos. If you have lots of one kind of reagent, slot that one and try unlocking its properties by combining it with reagents you have only in ones or twos.