Wintersaber Reputation is one of the hardest, most grueling reputations to raise in the game. It will require a few days work if you're extremly hardcore, or a few weeks if you're casually doing it. To get started you will want to head to Winterspring and speak to Rivern Frostwind. Below is a map of his location in Winterspring.
He will offer you the quest "Frostsaber Provisions". You will be required to collect 5 Shardtooth Meat and 5 Chillwind Meat. You can gather these off the Shardtooth Bears or Chillwind Chimera's. They both have a very low drop rate. You will need to do this quest 6 times until the "Winterfall Intrusion" quest becomes available.
Winterfall Intrusion requires you to kill 5 Winterfall Shamans and 5 Winterfall Ursas. The best place to farm these is to the east of Everlook. This is a long, aggrivating quest that you will have to repeat A LOT. This is the only quest out of the 3 that I find worth it to continually repeat. The good news is you will get a ton of Runecloth that sells well on the Auction House, along with Winterfall Firewater.
The good news is while grinding this quest, if you're on a PvP server you'll be able to exact your anger on the lowbies that come here to quest.