Starting zone
The starting zone is in the eastern plaguelands in the Eastern Kindoms. When you are there you will get your own starting gear and have no talent points. When you are questing you will get the talent points and new and better gear.You are under the rain of the Lich King and his a temp to rule all of azeroth. You will over through him and you turn good. You can not leave the starting zone until you do this and get 58.
Questing in the starting zone
The quest are really not that hard accusal they are very easy and fun. Compared to the very boring starting quest for any other class. If you have leveled all the way up to 55 it is very easy. The questing chain is not very long ether you will end at 58 when you over through the Lich King. Some people are better at questing than others so i am going to show you this full walk through by stevoman16 this was made in WOTLK days so some of the abilities maybe different but all the quest are the same it is broke up in to parts so I am going to give you the links to it http://youtu.be/ADiaJS585RM you can get the other parts in the description.
Talent
When leveling it really doesn't matter because all of the are great specs for DKs are great. Even though that they are good you can get the best spec for leveling. I prefer frost or blood depending on your personal preference. it doesnt really matter how u spec them because of the new Cata talent trees i will go in to more detail in my Blood and Frost pages that will be coming out soon.
Gear
The main gear that you will try to get for DK dps is to stack strength, crit, master, hit and other melee dps stats. If you are a blood tank you will get also strength but you will want also parry, dodge and stamina.