I started noticing several patterns that I consistently do while playing World of Warcraft. For example, whenever I go from Shattrath to another city to go to the Auction House, I always go to Iron Forge. Furthermore, I always visit the same auctioneer, the one on the left as you walk in. My bank alt (that's in charge of selling everything on the Auction House) has taken up permanent residence in Stormwind, where she always speaks with the auctioneer on the far right.
(The Stormwind stay started from when I would farm copper in Elwynn Forest. A level 26 bank alt pally has a lot of fun concencrating as she runs through the various mining spots in Elwynn Forest.)
I've only visited the Darnasus AH on the rarest occasions, but it's always the first auctioneer on the left. And if I visit the other Auction Houses, it's the person in the center as you walk down the ramp (Exodar and Gagdetzan).
As for banks, I faithfully visit the Aldor bank and guild vault on the left side only (as you walk in). If I visit SW, it's the banker on the left. And IF is the banker in the center, guild vault on the left.
My other alts have various spots to repair and sell gray items, but Leiandra almost always repairs her armor and restocks her reagents in Lower City near all the trade skill guys. (Keep in mind that she's a mage, so she never has her hearthstone set in Shatt.) If she only has to sell gray items, she'll do so in the Aldor bank area, the guy in the middle.
The whole point of all these details (and sorry if I bored anyone), is that I rarely deviate from these places. I'm just a creature of habit. Then again, aren't we all?
What are your obsessive habits in regards to NPC's?