The WotLK Death Knight charges in. He takes the first hit, soaks up the damage, and holds the foe in place while others beat on it. Avoid playing the Death Knight class if you prefer ranged damage or healing your teammates.
PvP
You’re going to have to learn how to play PVP all over again with the Death Knight. You will be effective once you get the hang of it. You will get a feel for it by practicing dueling and playing the battlegrounds at which point you can proceed with joining an arena team.
Raiding
Death Knights shine at raiding. They can tank as well as any class, and can put out high damage.
Builds
WotLK Death Knight talents are split into 3 categories, each of which are fully capable of supporting either a tanking or dps role:
Blood: This tree primarily amplifies the Death Knight’s melee spells, weapons, and abilities, and has a prominent health-regeneration theme.
Frost: This talent tree has a powerful critical strike/bonus damage them and many talents that add physical damage mitigation.
Unholy: This tree has a heavy focus on diseases and related abilities, as well as improving summoned minions. Also has AoE, spell damage shielding, and mobility-improvement sub-themes.
Suggested Professions
As a plate mail wearer, the WotLK Death Knight would do well to choose Blacksmithing as a profession, with Mining as a complement.
You probably won\’t need a gathering profession since you need to have a level 55 character to unlock a Wrath of the Lich King Death Knight. If you have gold to burn on leveling your Death Knight’s profession, consider Blacksmithing and Enchanting to run around with effective gear while you level.