You are entitled to two "professions." No more. However a few skills are not considered professions. Fishing, Cooking, and First Aid are all considered "secondary skills" and don't count against your two. The actual professions can be divided into two groups: gathering and production. Almost every production skill has a gathering skill necessary to do it…you don't *have* to be an herbalist to do alchemy, but you're going to be buying a lot of herbs from other people if you don't.
A few notes on the individual tradeskills, both professions and not…
Herbalism collects herbs from flowers, bushes and roots that spawn in the zone. When you take herbalism as a profession, you will get an ability that lets you detect herbs on your minimap. You will find that in the basic tab of your spellbook. Gathering herbs from a plant is as simple as right-clicking on it, but make sure it's safe nearby! You will get 1 to 3 of whatever herb comes from the plant you are picking. If you fail, you can try again at no penalty.
Mining is like herbalism, except that you gather ore, stone, and gems from ore veins. Again, you get an ore detection skill. However, you must buy a mining pick to gather any resources from an ore node. Those can be bought from any basic trade supplies vendor. You do not need to equip it. Ore is found almost exclusively in hilly areas and underground. If you are a Night Elf, be aware that there are ZERO ore deposits in Teldrassil - it is, after all, a giant tree.
Mining also includes the ability to smelt the ores you collect. Go to a city and find a forge, and you can convert copper ore into copper bars. Smelting does not affect the stone you quarry or the gems you find.
Skinning is collected from creatures you or others have slain. After looting a corpse of a creature that can be skinned — almost always a "beast" — the game will indicate that the corpse is skinnable. You must have a skinning knife in your inventory, also buyable from a trade supplies vendor. The creature also must be FULLY looted, which can make skinning in a group a nuisance. In general, skins are much more widely available than herbs or ore, but leatherworking requires large quantities of leather, so there is no direct advantage there.
Fishing is the most unique of the gathering skills. Find a body of water, equip a fishing pole (bought), and select fish. Somewhere in the water, a fishing bobber will appear and eventually it will make a small dip to indicate you've got a bite. Right click on it to try to reel in your catch. When you first start off, you will get easily frustrated at the amount of catches that get away, but once you get your skill to 30 or so, it goes MUCH more smoothly. Make sure you start in very low-level areas, because the skill level required goes up very quickly.
Those were the gathering skills. Here's what you can do with them.
Smithing uses mostly ore to make weapons and heavy armor, as well as a few other metallic odds and ends like skeleton keys, shield spikes, and sharpening stones. At higher levels, smithing can specialize into weaponsmithing and armorsmithing. Smithing requires a smithing hammer and must be done at an anvil.
Leatherworking produces leather armor and armor kits for slight improvement of the armor rating of equipment. Some leather items are not made wholly from leather and vendor items; you will occasionally need other random animal parts such as murloc scales, or an alchemy potion related to the item. At high levels, leatherworking specializes into Elemental, Tribal, or Dragonscale leatherworking. You can only pick one.
Tailoring creates clothing out of cloth. There is no gathering skill for getting cloth. Instead, one must gather it from humanoid creatures. Any time you kill a defias bandit, a furbolg, a scarlet crusade member or a venture co. miner, for example, you have a chance to get linen. Higher level creatures will eventually drop the more advanced types of cloth. If any gathering skill goes with tailoring, it would be skinning, since tailoring can also make bags with the inclusion of some leather. This is fairly minimal though. Tailors are generally free to choose any second profession they want, and many become enchanters since that skill also stands alone.
Alchemy makes potions from herbs. Potions take on two varieties - potions that give short term effects, such as a potion of agility, and those that give immediate effects, like a healing potion. Because the act of gathering herbs is more labor-intensive than many non-herbalists realize, the market for potions is not as strong as it could be, but there are select potions that consistently sell well to players. Some potions require non-herb components, usually in the form of oils derived from fish. Thus, alchemists will often take up fishing, but this isn't a necessity. Alchemy potions are also used in several recipes among the other production skills, such as an intellect potion being used for a tailoring robe intended for mages.
Engineering is the strangest tradeskill. Strange, because most of the items it makes require you to be an engineer to use. This makes it a popular choice among people who want to be able to do everything, since they can let somebody else do the work for other tradeskills. Engineering is especially popular among paladins who have no ranged attack and can lob the bombs it makes, and hunters who enjoy the benefits of self-made guns and ammunition. There are all kinds of other quirky items engineers can make though, from target dummies to gnomish shrink rays. Engineering also produces head slot items potentially before you could acquire one yourself, since head items tend to have at least a required level of 20. Engineered items primarily - but by no means exclusively - are made with mined ore.
Enchanting is the often-forgotten tradeskill because, to steal a company's tag-line, it doesn't make the armor you wear. It makes the armor you wear better. Enchanting is not a skill to take lightly: it is highly expensive. The components gathered for enchanting are created by the enchanter by DIS-enchanting other magical items. Generally speaking, this means items that have any stats on them besides just damage for weapons or just AC for armor, which you would ordinarily sell in the auction house for money, instead gets destroyed to make enchanting components. It is also thought by many to be the most powerful tradeskill because of the way it can enhance everything else. Since many tradeskilled items beyond the basic starter items have magical properties to them, an easy way to get items to disenchant is to take them from someone who is mass-producing a particular item to raise their skill level. Enchanters can freely take another tradeskill, so tailoring with its lack of gathering skill is appealing in this regard.
Cooking makes food from, well, foodstuffs. Killing creatures often gives some kind of meat or giblets or whatnot. Fishing gives fresh fish that can be fileted. Cooking can be very handy for a soloing warrior or a hunter that is trying to keep his pet fed. Sadly, food only restores HP and not mana, and there are only a few select recipes that don't just regenerate health beyond the "well-fed" buff that cooked food gives. (This adds some spirit and stamina to your character after eating cooked food, rather than bought or summoned food.) Cooking requires a fire to make items. There are fires in town or you can bring tinder to make your own on the road.
First Aid is another skill for non-healing classes. Cloth gathered from humanoids, rather than being used for tailoring, can be fashioned into bandages which can then restore a small amount of health. You can only apply a bandage to a target once every 60 seconds, and neither you nor the target can be getting hit during the bandaging.
So the question everyone always wants to know is, Which professions would be best for *me*, as a
Here are some of the common tradeskill combinations and who often does them:
Mining/Smithing: Warriors and Paladins for armor, sometimes Rogues for weapons
Mining/Engineering: Paladins for bombs, Hunters for ranged weapons and goblin jumper cables, everyone for the unique engineering-only items
Skinning/Leatherworking: Any leather-wearing class
Herbalism/Alchemy: Anyone who likes to use potions, often warriors or priests
Skinning/Tailoring: Cloth-wearers interested in being career clothiers and bag-makers
Tailoring/Enchanting: Enchanters looking for easy source of disenchantable items
Herbalism/Skinning: People who seek easy profit, since gathering skills have no overhead cost
Skinning/Mining: Same as above. Herbalism/Mining isn't normal since you can't have both tracking skills active at once.
Note that none of these include fishing, cooking or first aid since they do not count against your two profession limit.
As your skill increases through use, you will need to visit trainers periodically. Production skills can learn new recipes from trainers, and everyone will need to train to a new plateau at 75, 150, and 225. An apprentice trainer cannot teach you past the basic level, and will refer you to a journeyman. When you outlevel the journeyman's skill, they will suggest an expert, who will later suggest an artisan. There is only one artisan for every single tradeskill (per faction, anyway.) Enchanters in particular are a little screwed over because their artisan trainer is hidden in a dungeon rather than in a town!
Secondary skills are trained at the 150 point level by special books you have to buy from somewhere. For instance, the fishing book is sold in Booty Bay, and costs 1 gold. People often buy them for resale in the Auction House if you don't know where to go or don't want to go there.
Some recipes only drop randomly from creatures as loot, and some are sold from special "limited supply" vendors. Check the site's listing for each type of combine your skill can do. If it has a recipe listed, it does not come from a standard trainer.
Other general information about tradeskills:
You will NEVER fail a production combine. If you fail a gathering combine, you can simply try again, since the ore vein won't disappear until you harvest it.
Tradeskill difficulty is color-coded. Either the background of the item name in the production menu or on the tag of the item you are trying to harvest will be color-coordinated. Something that is an average challenge for you shows as yellow. Easy items you are unlikely to gain skill from are green, and gray are trivial. Challenge items you will almost definitely gain skill from are orange. Red items cannot be attempted. You'll note that this color arrangement extends to quests in your quest log, and to the level of creatures you have targeted, to a similar effect.
Any item that is not clearly part of a quest or a worn item, but has its name in a color other than gray, usually white, is used for *some* tradeskill recipe. Items you find on creatures such as large fangs and goretusk livers might not *seem* like tradeskill items, but their name will be listed in white because they are used for alchemy and cooking, respectively.
While you can only have two professions, you are not locked into them forever. You can abandon a tradeskill by pressing K to get to the skills menu, finding the profession on the list and clicking on it, and then clicking the small "no" sign at the bottom of the window to unlearn it. At that point you can pick up a new skill. If you ever return to that skill, you will have to begin from scratch, and this does not clear your specialization choices.