I've been collecting some Auction house Posts. Here they are with some interesting or representative excerpts:
Auction House Basics
Deposit Fees. All auctions will be initially charged a deposit fee. The deposit fee is refunded upon the successful sale of the item. All successful sales are charged an auction consignment fee which is extracted directly from the final sale price. All fees are higher in Gadgetzan.
Auction House Tips
Sound. You can hit control-s to disable the sound effects if someone is making really annoying sounds in the auction house. Don't forget to re-enable them after you leave.
Auction House Formulas
Don't lower your starting bid below 70% of the suggested amount. (70% in a factioned auction house, 79% in the neutral house.) Otherwise you risk getting less money for an item than a normal merchant would give you.
The Dressing Room Feature from Patch 1.7
WorldofWar.net's Auction Houses Guide - Includes a link to Auction UIs/Mods
Bid increments are 5% of the current bid When a bid is made a minute is added to the auction duration.