You have to have 2 professions already. Inscription has to be at least level 400 and one of them.
Anyways, use any Master Shoulder Inscription (example in screenshot). Keep on doing that on a shoulder item and until your enchanting is level 400 (you don't have to be an apprentice or trained in enchanting in any way), then go to the Grand Master enchanting trainer and train for Grand Master and level it up to 450 and bam, you have 3 professions. Yes, this does mean Inscription and Enchanting have to be 2 professions but if you're serious about getting the most out of your gear you should have been eying those 2 already. Good luck.
Proof in screenshot.
http://screenshot.xfire.com/screensh...ca7ad315df.png
NOTE: This was done on 3.0.9 WoTLK.