The basis of this tip is supply and demand of Herb's on the Auction House.
Some people do not farm their own herbs, or do not have the patients to wait for more items to be posted on the Auction House or do not know the average price per stack. This is why this works!
What the idea is, You find Herb's on your Auction House that has a low supply.
Step 1) Search Trade Good's -> Herb.
Step 2) Search for a low supply of high end herb's (Outlands).
(On my server I see that Mana Thistle has a decent supply. I would prefer it be a lower supply but for this guide I will buy them out.)
Step 3) Buyout all the of stacks of 20's - (Mana Thistle in my case).
Step 4) Visit Wowhead and search for the Herb that you had bought out.
As you can see, 3 Mana Thistle's are used in each flask and 7 Mana Thistle per Cauldron. Post some of your Mana Thistle in these amounts. I am going to do 5 stacks of each. (Note: Post the rest of the stack's in 20's or wait for the stack's of 3's and 7's to sell out.) I will be posting the rest in stack's of 20's.
If your worried about people flaming you for raising the price of the item, you can also post them on different characters. (I bought 12 stacks of Mana Thistle each, split up the stack's between different characters. So that one character doesn't repost all 12 and appear to "Flood" the auction house) And if you go to this extent you might as well undercut yourself by a few copper to lower suspission. I personally do not go to this extent because I personally don't care.
Note: I bought the Mana Thistle at 12g-15g. I will now be posting the stack's at 19.99g. It is not as big of a profit I would like but it is still a profit. I normally work with more expensive herbs (Nightmare Vine, Fel Lotus etc). To where I have gotten 10-15g more per stack. (Not stacks of Fel Lotus).
Here are the Mana Thistle's Re-posted. As I am the only one on the Auction House with Mana Thistle's they should/will sell out quickly.
I hope someone found this tip useful.
Thank you for spending the time and reading this.
As it is against the rules to post non-Auction House information in this thread, feel free to PM me if you have any questions.
I made this guide a while back, but it still works for me so it deserves to be in this thread.