Northrend Exploration Achievement Guide
Explore Sholazar Basin: Explore all of Sholazar Basin.
Explore Storm Peaks: Explore all of Storm Peaks.
Explore Howling Fjord: Explore all of Howling Fjord.
Explore Crystalsong Forest: Explore all of Crystalsong Forest.
Explore Icecrown: Explore all of Icecrown.
Explore Zul'Drak: Explore all of Zul'Drak.
Explore Grizzly Hills: Explore all of Grizzly Hills.
Explore Dragonblight: Explore all of Dragonblight.
Explore Borean Tundra: Explore all of Borean Tundra.
Northern Exposure: Kill one of the extremely rare hard to find Northrend creatures listed below. This achievement requires you to find and kill one of the super hard to find mobs in Northrend. Your best bet for this achievement would be to pick one of the mobs from the list, look him up, find out where he is and farm in that area until he spawns. Or if you're lazy and you are only going for the achievement, look them up one by one and search each location.
Frostbitten Achievement Guide
Frostbitten: Kill all of the extremely rare and hard to find Northrend creatures listed below. Unlike the other achievement, you will have to find and kill ALL of the rare monsters. I've split this one achievement into two sections. The first will cover how to fly over each zone specifically looking for the mobs. The second will cover each rare mob individually. Use the section that best suites you.
Icehorn, Old Crystalbark and Fumblub Gearwind in Borean Tundra