To some this may be considered common sense but I have made lots of gold and have had Little to None competition in the AH selling certain Item Enchantments.
Item Enchantments are basically things you can enchant your character with. From Cleft Hoof Leg Armor to Brilliant spell Thread it all makes good gold.
All the Item Enchantments I have made gold from include~
BC Item Enchantments
Clefthide Leg Armor
Cobrahide Leg Armor
This item enchantment sells the best out of all of them. I do not know why but on my server this always seems to be the one that is easiest to get rid of. I can usually get away selling these for 100-150g. Cobrohide Leg Armor is a pain to make because no one farms the cobra scales anymore but when I'm bored I well go out there and farm my own at times.
NOTE: I do not recommend selling the epic quality version of these items. On my server they sell just as good as the blue ones. I have wasted a lot of gold making the epic ones and they are really hard to sell. I have had a few sit in ah for WEEKS. But maybe on your server it's a little bit different.
Epic Quality Item Enchantments
Sapphire Spellthread
Brilliant Spellthread
The price of eternal fires have been real low lately, and with frozen orbs dropping below 30g each I can make these for under 100g and sell it for over 200! Sadly, eternal life has been costing a lot, but I still make a pretty good profit. I farm my own Iceweb Spider Silk for this.
Level 80 Blue Quality Item Enchantments
Shining Spellthread
Azure Spellthread
The matts for these two are really cheap. I have made a lot of money by making these. I find that this is way better than the epic quality item enchantments. I can get away with selling these around 50g each. On my server they have a dead market and no one posts them.
This is just a quick guide. For those of you that don't know i keep a notepad file of the items I buy and sell. Most of this is just server dependent but I thought this could work for the majority of servers and decided to share. I hope this helps some of you out.