Engineering is a very fun and creative Profession. You can create all kinds of wacky things that are fun to use and also entertain and amaze other players. Engineering is used to assemble metal and stones into parts needed to make explosives, guns, scopes, bullets, mechanical dragons, aquatic helmets, and much more. More than any other Profession, engineering products require several steps to be completed. Most items created by engineers can only be used by engineers. You can sometimes create something you can sell to another engineer. Many engineering recipes require a lot of different parts before the item can be created. This will require more space in your bags than other Professions.
If you plan on being an engineer, you should probably already be a miner. Miners collect ore and smelt ore into bars to create the majority of engineering items. Engineer recipes often include jewels, which are found in a variety of places. Typically, most engineers buy or are given rare jewels from other players. The auction house is a good place to buy gems if you can't mine them yourself. Some engineer recipes require leather, which you will need to buy from a skinner or the auction house. You will need to find a lot of other odd ingredients for your recipes that might need to be purchased from other players. Some items can actually be fished up with the fishing skill or found from monster drops or treasure chests.

Becoming an Engineer

First, you need to find an engineering trainer. Ask a guard for directions in a big city. After you have learned basic engineering, open up your abilities book (hit 'p') and look for the "Engineering" icon that has been added to your abilities.

Sample Engineering Items

These sample items might convince you it's time to become an engineer:

- Coarse Dynamite - Inflicts X to Y damage in a Z yard radius.
- Big Bronze Bomb - Inflicts X to Y damage and stuns targets for Z seconds in an N yard radius.
-Mechanical Squirrel - Create a mechanical squirrel that will follow you around as your pet. It serves no purpose other than to entertain people. You can hand out the squirrels to other people as gifts or even sell them. "It doesn't do anything, but boy, it's cute!"
-Small Seaforium Charge - Use an explosive charge to open simple locked doors.
-Goblin Land Mine - Places the Goblin Land Mine on the ground. It will explode the next time a hostile creature passes near.
-Explosive Sheep - Summons an Explosive Sheep which will charge at a nearby enemy and explode.
-Goblin Jumper Cables - Jumper Cables will sometimes be able to shock a dead player back to life. Be warned that they are experimental and may explode.

Additional information

Schematics
The engineering trainer has some very cool engineering plans. However, there are many more interesting and desirable plans out there to find from monster drops. You will likely have to buy these from other players or get them from friends if you aren't lucky enough to get them yourself. You can also find them at the auction house, treasure chests, or by gaining reputations.
Gnomish and Goblin Engineering
After you think you have mastered Engineering, you are offered a chance to specialize in either Gnomish or Goblin Engineering. You must first reach 200 skill and level 35. Alliance players can then speak to Lilliam Sparkspindle in Stormwind City. Horde players can talk to Tinkerwiz in Ratchet. Then you will be offered some quests to open new recipes for that school of engineering. Oglethorpe Obnoticus is the master Gnomish trainer and is found in Booty Bay. Buzzek Bracketswing is the master Goblin Engineer in Tanaris, Gadgetzan. Once you've selected your side, you cannot switch to the other. You should choose based on what recipes are available. There are some very cool and unique recipes for each side. You have to pick which ones you like the best. It can be a hard decision, they're both good


Link: http://www.wowhead.com/?spells=11.202