Always sell all items on Auction House. If you are not sure about its value, then check the market. There are some risks that item won’t be sold and you will lose money just putting it on Auction House. Good idea to make bank low level characters and keep everything there until the weekend. All sales increasing on Friday, Saturday and Sunday. Besides, you can advertise in a trade channel to inform people that an item you are selling has been put on Auction House.
Why Skinning? Skinning is incredibly easy to level up while you are leveling your character. The leather that you skin will almost always sell on the Auction House (albeit not for much, but hey– it’s free gold!). Even if you don’t want to take the effort to sell the skins on the Auction House, you can simply vendor them for a significant amount of extra gold.
Leatherworking has three specializations: Elemental, Tribal and Dragonscale. I’d pick up Tribal one. It allows to craft Devilsaur set items. Hunters, Rogues, Warriors, Feral Druids, even Enhancement Shamans and Retribution Paladins are among your potential clients. On any realm there is Un’Goro Mafia on Horde and Alliance, they control whole Un’Goro Crater zone and farm Devilsaurs 24/7. They are making thousands of gold. With Dragonscale Spec you are able to craft Black Dragon Mail set. Good demand as well among DPS classes Warriors, Hunters, Shamans, Paladins, for those who wants Bis Pre-Raid items fast and easy.