So you've heard all about Achievements, the latest feature to be revealed from the Wrath of the Lich King. Blizzard's official Achievements page mentions over 500 different Achievements that players can pursue. There seems to be an Achievement for everybody, depending on your play style and how you enjoy the game. MMO Champion and the WotLK Information Wiki both have comprehensive lists of all the Achievements currently in the Wrath Beta.
The lists are a great read if you want to plan out how you can go about completing those Achievements, from the simple tasks, such as completing five daily quests (worth 5 points), to the loftier goals such as defeating the 25-man Naxxramas with only 20 people (worth 50 points). Achievements are classified under different categories, such as General, which involve collecting vanity items or finishing "whimsical" goals; there is the Quest category for those who are obsessive questers; there are also PvP goals that involve specific tasks in the Battlegrounds or Arenas.
There are also subcategories per category, breaking down Achievements even more for those meticulous planners. The Dungeons & Raids category, for example, is broken down into three subcategories: Classic, The Burning Crusade, and Wrath of the Lich King. Classic Achievements involve goals in pre-expansion Azeroth, such as killing Archmage Arugal or Edwin VanCleef (each worth 5 points), while The Burning Crusade Achievements expectedly call for the demise of bosses in both normal and Heroic difficulties.
It's impressive how much data Blizzard's game actually tracks, with some miscellaneous achievements tracking the most obscure statistics such as the number of Healthstones a character has consumed, or the most expensive auction she has ever sold or bought. Some are plain statistical trackers which are expected to fluctuate over time, like biggest crits or heals; while some goals are more specific, such as The Cake Is Not a Lie, wherein the character must bake a Chocolate Cake.
There are some curiously notable Achievements that jump out. One, in particular, falls under the Quests category and is entitled Tuskarrmageddon, requiring the player to 'mindlessly slaughter 1,000,000 Tuskarr'. The Achievement is worth 100 points with a note about a reward called "Baby Seal Club", which sounds appropriately gruesome. Some Achievements are tiered, with each task more difficult than the last. Players interested in vanity pets can challenge themselves first by getting one in Can I Keep Him?, and later graduate to ten pets with Plenty of Pets, or fifty pets with Pandemic of Pets! The ultimate pet collector's Achievement is Shop Smart. Shop Pet... Smart, which demands a collection of 75 vanity pets! Are there even 75 in the game? Good luck with those bank slots.
Speaking of bank slots, Achievements track those, too. The number of bank slots your character has, or the number of unique tabards your character owns, the number of times a Shaman has raised your toon from death... it might even be an Achievement to not achieve anything, as it's almost impossible given the events that the Achievement system tracks. Even embarrassing statistics like the number of deaths are tracked. Want to run against the grain? How about dying over and over through falling? Because yeah, the Achievement system seems like it tracks that, too. Head on over to MMO Champion or WotLK Information Wiki to look through the Achievements, there's bound to be something that fits your character's goals perfectly.