To all the Death Knight's (dk's) out there...of whom I am one...
First off:
If you are a dps dk most people will think you are a noob. They are right. The only way to prove them wrong is to put out the dps. 2.0k in raid. 2.4k in H's.
If you are a tank dk most people wil think you are a noob. They are right. Know the fights in and out, tank well, and have fun. People like those kinda of tanks.
2nd:
If you are a dk: SHUT UP. People will not listen to you or care to. Why? Because they think you're a noob. (and they're probably right) So go with the flow and be quiet. People enjoy a quiet instance without lots of chats or vent. This makes for less headaches.
3rd:
If you are a dk you will get invited to guilds, but not always to their raids. Why? Glad you asked. Your dps sucks, even if you are geared enough for the raid, you dps sucks. Gear will not always make or break you, your rotations, talents, and glyphs will. Find the right combination of those 3, while still doing H's for better gear, and you'll start dpsing more guaranteed. The best way to show your stuff is to run with the officers and the other higher ups of the guild. They will make the decision if you go or not, so show them you have the dps for raiding. The easiest place to do this is in H's.
4th:
If you are a dk you're asking how can i find this combination and gear? Good question. GO TO H'S!. There you can dps your heart out, pick up all the plate dps gear you can, and figure out how to play a dk. A dk isn't a toon that is easy to play. He is easy to level and have fun on (Believe me, I know), but to dps in raid is something completely different. Figuring out your toon in 25 levels=hard. Figuring out your toon in raids=Fail. But figuring out your toon in the end=uber dps.
Hope this helps.