Bit of help is never wasted. The most basic, where to find new 5 man instance is currently most asked question in chat. So i am here with helpfull hand. Err. Helpfull picture. And of course, something more - strategy.
Does the question "where the hell is entrance" sounds ridiculous? Actually it is not. Everybody should know where Icecrown Citadel is - if not, it's easy to see on the map. But entrance to new 5man instance set is cleverly placed on ridiculous place and hard to find. Well, here is easy help - see the picture.
The entrance in "ground" level is to 25 man. To 5 man instances (three wings) you have to fly a bit up and get there from western side. Clever, right?
And while you are inside, you should know that on left side is "The Forge of Souls" - the place, where you should start (and yes, Jaina Proudmore is inside with quest which you need to get done for "attunement" for all three wings).
Then middle entrance is to "The Halls of Reflection" and right one to "The Pit of Saron". Good to know after wipe. If you start from left and just follow the quest line, you will be ported from one instance to other - possible wipe might lead in slight confusion. Also because the actual order is Forge of Souls -> The Pit of Saron -> The Halls of Reflection. Well, it's Blizzard after all :)
tank in middle, others stay behind. Watch for spawned "Corrupt Soul Fragment" and don't let it reach boss (good idea is to move boss away). At 30% boss teleports in middle and creates Soulstorm - hug boss, be prepared for fear (healers heal the one feared) and don't forget to get back immediately.
tank and spank, watch for Mirrored Soul spell (stop dps at that moment). Well of Souls is usual crap on ground, where you should know that standing in anything like that is not good idea. Beware of Wailing Souls spell - just don't get in front of boss. Unleash Souls spell seems easy, just spawns many mobs with low hit - just kite them around (they cannot be attacked anyway).
Keep on the right, killing any Laborers or anything that is in your way - don't forget to free the slaves in case you are on quest chain. Shortly you will arrive at first boss.
Just pull boss and adds, aoe them down. Spread and watch for "Throw Saronite" - the remains on ground are important to get rid of Perfmafrost debuff (just hide behind saronite pack to get out of sight). Should i say that you should not get hit by flowing saronite?
At 66% and 33% there will be 2 sec stun for all members and boss will leap over to other anvil - tank should get him (but not before he gets rid of Permafrost debuff). Easy.
Continue on right side, but do not take path uphill, just on left side of path is second boss - go get it after you clear the area around him.
Anyway, he is very funny and bit harder if you aren't used of moving, moving and moving. You will be killing Ick (Krick, the gnome, is just sitting on him). Just listen to Krick :
"No, that one! That one! Get that one!" means random member will get chased - kite him, stay out of his range (important, as he has double damage buff). Takes 12 second, then you are safe.
"Quickly! Poison the all while the're still close" is obvious reason to move away from boss. Casting time 5 seconds. So hurry.
"Enough moving around! Hold still while I blow them all up!" is another run for your life. Mines will be spawned at your current position, so keep moving, avoid existing mines (they just grow and blow).
After 2nd boss is dead, head uphill until you arrive at tunnel - it's gauntlet like event. As usual, dont stand in ice circles on ground. In fact, just run to middle of tunel (tank picking up mobs) where is metal platform - it's safe place from falling ice. Just AOE everything down (including Glacial Revenenant on heroics).
is attackable even when mounted, but target him, not his mount (which is not attackable at all). It's again about moving and controlling your dps.
Rimefang, his dragon mount, will shoot frostbolt at random player (usual tactics, move away) and create a patch of ice on ground. Tyrannus will cast Overlord's Brand on player - that player must stop damaging Tyrannus (will damage tank instead) - if healer has this debuff, stop healing as any healing heals Tyrannus (with amplification). Tank should watch boss for Unholy Power (empowerement) in which case he should kite Tyrannus immediately to closest ice patch on ground (it slows him greatly down and allows further kiting) - lasts for 10 seconds. Healers keep tank topped as there is occasional Dark Smash with large damage spike.
Beware, Lich King is awaiting you. And Jaina Proudmore? She is a poor girl still in love with something that is deep inside Lich King head.
Not exactly easy fight on heroics as you can get wipe easily - there will be four waves of mobs, boss, short quite period where you can drink, again four waves, second boss. Waves are nothing special - Priest, Mage, Hunter, Warrior, Rogue. Use crowd control, kill them fast and think (really) about your mana. Either stay in corridor where you entered the circular room (tank before all others to pick everything that moves) or just move to one side of room (you can stay on any of bosses, as they are not attacking you before their time is). Usual "kill the healer first" is good idea. Of course.
Tank and spank, nothing more - and you should kill him fast as he gets help from Hopelesness where your damage and heals are getting worse and worse. Worth of watching is AoE fear which does also some damage.
Nothing much different from Falric, just don't be stupid and watch ground - move away from Well of Corruption. It's advisable to not remove Shared Suffering (removing it will do damage to target and nearby allies, on heroics its normally 40K/12sec, easy to heal through).
After this (i would say nice) fight continue to third boss, piece of cake. And btw, if you wipe on first two, you might need to disband and for your group again.
Fun is in reflections of every party member summoned by this "boss" - kill them alongside with boss. Nothing hard.
Most funny part of this instance is "Running from the King" - no, you will not fight Lich King. Instead you will be running - long way. Again there will be several waves of mobs (more and more of them). Of course you can try and attack Lich King, but 23M HP is good reason to forget this silly idea.
Running is fun, just run to ice barier (Jaina or Lady Sylvanas will take care of them) and kill the wave trying to kill you and your faction champion (Raging Ghouls, Lumbering Abominations, Risen Witch Doctors)
There is faction ship at end with chest with final rewards. Currently bugged as ship can be entered only with levitate from priest - touching stairs leads to disconnects. Also walking on ship is not advisable - leads to disconnects on various places.
Use portal to get back to Dalaran.