Here are a couple of links you can take a look at:
http://wow.toshimo.com/viewtopic.php?t=278
http://www.xs4all.nl/%7Ebrt/wow/guides/skillupengineering.html
Here are a couple of items from the first link:
5.5 What are the different levels/ranks in the professions?
Rank (Min - Max Skills)
Apprentice (1-75)
Journeyman (50-150)
Expert (125-225)
Artisan (200-300)
Note that gnomes gain 15 skill in engineering as a racial bonus. As such, their maximum skill at each rank is increased by 15. (90, 165, 240, 315)
5.9 What's that racial level you just mentioned?
When you have both reached level 30 and have 200 engineering skill, you may choose to become either a Goblin engineer or a Gnomish engineer. One path excludes you from the other, and there is no way to change your mind once it's been made. This choice is done through a quest, so once the quest is done you cannot do it again to change your mind.
The quest starts in one of three places: Ironforge, Undercity, and also in Ratchet.
You will receive a book to read about the differences between the disciplines. After you've made your choice, you must visit the master for that path. The Master Gnome engineer is in Booty Bay.
The Master Goblin engineer is in Gadgetzan. These trainers will give you a task to complete to join that society. Note that you don't need to choose either, as it is not linked to learning artisan engineering at level 35 at all.
For Goblin engineering, you must provide him with 20 Big Iron Bombs, 20 Solid Dynamite, and 5 Explosive Sheep.
(Note! This is the number of items, not the number of "cycles" through the schematic. Pay attention to how many are made each time. I made WAY too many when I did this.)
For Gnomish engineering, you must provide 6 Mithril Tubes, 2 Advanced Target Dummies, and 1 Accurate Scope.
These trainers are NOT, I say again NOT the Master engineer needed to further your progression. Completing this quest does NOT raise your skill limit past 225. Choosing a path simply gives you access to special schematics while excluding you from the others.
5.12 I am ready to train in Journeyman/Expert/Artisan, who can train me?
You must find the engineer designated as the skill level above what you would like to learn. That is, to learn journeyman engineering you must train at the expert engineer. The journeyman is not skilled enough to teach you what he is still learning, and the artisan can't be bothered to teach someone with so little skill.
Engineering trainers are usually found in major cities.
Artisan engineers can be found in Orgrimmar and Ironforge.
The single master engineer (for all engineers) can be found in Gadgetzan in Tanaris. His name is Buzzek Bracketswing.