It was a little easier to keep track of your progress in Cataclysm's largely linear zones, but Pandaria's zones offer you more freedom in what you're completing and when. To that end, the world map now shows you nearby quests on the world map. It isn't zone-wide, but it does work in a fairly large radius around you, so if you're flying or riding around and check your map periodically, you can see any unclaimed and available quests.
It's worth noting that Pandaria's Loremaster achievements are based on quest lines completed, not an actual number of quests, but this should definitely help you track down each story to add that tick to your achievement.
It's open warfare between Alliance and Horde in Mists of Pandaria, World of Warcraft's next expansion. Jump into five new levels with new talents and class mechanics, try the new monk class, and create a pandaren character to ally with either Horde or Alliance. Look for expansion basics in our Mists FAQ, or dig into our spring press event coverage for more details!