Stick down DnD on AoE pulls (and even single-target) as a pre-emptive strike for threat, do this as you're opening in on the target.

For glyphs you want Death Strike, Rune Strike and Heart Strike (Prime Glyphs) on single-target, swap out Rune Strike for the Death and Decay glyph on AoE fights. Good Major Glyphs would be Blood Boil for AoE, Rune Tap (helps healers), Vampiric Blood, and Anti-Magic Shell. Dancing Rune Weapon glyph is rather meh.

For the skills to use: DnD on pull. Then you basically just spam Death Strike and Rune Strike. Heart Strike and Blood Boil are good for AoE (Heart Strike has a cleave effect) and I never use Death Coil unless the target's out of range. Diseases are optional and I only generally keep them up on bosses or with Outbreak only as the damage is rather pitiful on anything else.

I'd suggest you tank normals, to begin with, as well. Even if you've got the tank gear to do Heroics you'll still want some practice in normal dungeons until you've got some practice.

This article on WoW Insider might help you, one thing you'll want to learn (nobody can teach you this) is situational awareness. Watch where mobs are and what they're doing, watch any AoE damage (AMS is handy for this) and also watch your own threat and the threat of other players.

Sorry, forgot the article link:

http://wow.joystiq.com/2009/06/03/wow-rookie-tanking-for-beginners/

Thanks for the tips!

Short summary - fights vary.
Start on normals, not heroics. Even if you are geared for heroics.
For multiple mobs in general - Drop Death and Decay on top of yourself and Death Grip the caster to you (or ranged - in fact if there is a hunter type mob in the enemy group, its better to death grip him and strangulate the caster). The rest of them will run to you through your death and decay and by that time you should have diseases up on the one you death gripped and can now spread to the rest with pestilence. After that it's what others have said. Try to keep blood shield up with Death Strike, Rune strike when its available, Heart Strike in between those. Keep bone shield up whenever its off cooldown. Blood boil when its a free one or if you need help gathering aggro at beginning.

Opinions vary of course between tanks but this is a general strategy and will get you started until you find your own groove. Tanking is fun and we need more of them. Sometimes you are the hero, sometimes its thankless. Good Luck!