Blood Death Knight - Advice on Starting Out?

To learn about tanking the one thing most important to you is learning how to create and maintain threat. You need to learn your best threat abilities. At 58 you don't have all the tools yet.

You get your big threat spell at 60 I believe with Death and Decay. Up until then blood boil works well for snap aggro. Heart strike is a cleave and when glyphed strikes 3 mobs. Right now a lot of people are playing a diseaseless blood tank. They are avoiding talents that benefit from diseases.

Reason being is, as you apply diseases to your main target all others youve aggro'd will start to lose aggro on you.

At 58 I would pull with either icy touch or Death Grip, blood boil and then heart strike away.

At 60 when you get DnD, drop DnD, pull your favorite way, blood boil, tab target using what ever and until your heartstrikes and blood boils are up.

As already mentioned, don't worry about diseases as Blood while leveling.

Death & Decay isn't as potent as it used to be, and with no diseases up it's even weaker for Blood. It's a nice addition, but my no means needed anymore.

When you pull use Icy Touch, if you have Rune Power from the last fight use Death Coil instead. Avoid pulling with Death Grip unless it is a caster. The reason I say that is because you will want it available if something goes after the healer, tries to run away, there are multiple casters, etc.

You can tank right off the bat now with the way the new talent trees are. Glyphed Heart Strike will be your number one ability. For groups of 4 or less you can just tab around to different target hitting each one.

For Snap Aggro or larger groups Blood Boil + Glyph + Various Talents will be your best friend.

Death Strike is a great ability and should be used pretty much whenever you have the runes available. But it is of lower priority while leveling since it doesn't hit multiple targets, and the healing from it will be mostly unneeded until you start hitting harder content.

Once you get Rune Strike it will become your highest priority since it does decent damage & lots of threat. Mix it in with Heart Strike while tab targeting, or to "seal the deal" on anything you pick up. It will help keep things glued to you.

A great place to start is the DK 4.03a Tanking Guide on wowhead. Explained everything form the basics and talents, to raiding and some theory.