Morchok is a relatively easy boss, but he does have a few abilities to watch for. The first is Crush Armor, which reduces the tank's total armor. If you're tanking the fight, be sure to set up a swap with your fellow tank -- whenever one of you reaches four to five stacks, ask for a taunt. (Make a macro that says "/raid Crush Armor stacks are high, please taunt" or something to that effect, if you need to.) Then, once your partner's armor stacks are just as high, if your stacks have dropped off, taunt back.
Stomp is the next ability, which does some AoE damage split evenly between all players within 25 yards. We don't have to worry about this too much, since we'll always be within 25 yards, but there is a caveat -- the two players nearest the boss take extra damage. Honestly, as a DPSer, if I have full health, I sometimes like to slap on Icebound Fortitude and move close enough to take the extra damage. It won't kill me, I'll be alive, and if the current tank has a high Crush Armor stack, it may just save his life. It's not mandatory, of course, but it's an idea. Of course, the opposite applies. If you're relatively low health when the Stomp comes, you may want to back off a yard or two just to ensure you aren't hit with more damage than you can take.
The Resonating Crystals Morchok throws out require seven people to be right up on top of them to make them explode with people taking the minimum damage. If you are far away from the crystal and are targeted by one of its rays, you will take a lot of damage. In a perfect group, your ranged players will take care of this, but if it looks like they aren't and you're DPS, don't be afraid to pick up the slack and run for a crystal. Sure, your DPS will go down, but you may keep the raid alive. Tanks should, of course, avoid the crystals. They have other sources of damage to deal with.
From time to time, Morchok will pull everyone toward him and stun them. As soon as the stun drops, he will begin to bleed, and this blood will do major damage. You can mitigate this damage a bit with Anti-Magic Shell, but you will want to run out of it and to the stones at the sides of the battlefield. If you hide behind these stones, you can avoid the blood and (if you position yourself just right) throw a few ranged attacks at him. Once the blood disappears, you can run back in and engage him.
Warlord Zon'ozz is a relatively easy encounter for Raid Finder. Tanks just need to tank him facing away from the raid so that he doesn't hit the DPS with his cone attack. Honestly, you can probably get away with one well-geared tank for this encounter, but if his Focused Anger or Psychic Drain takes out one tank, it may be good to have another tank waiting in the wings too. That said, if you use two tanks, the off tank should stay behind with the DPS until needed to avoid healing the boss.
The other major thing Zon'ozz does is summon a ball called the Void of the Unmaking that must be bounced between the ranged and melee players until it has built up stacks and can be bounced at the boss. The bounce mechanic is a bit more forgiving in Raid Finder mode, doing less damage to the bouncers, to the point I have seen some raid groups simply assign two people to bounce it back and forth.
Try to get to it bouncing between your ranged and DPS groups, and assign one from each DPS group to make sure it's properly bounced, and you should do fine. Once it hits about 10 stacks, you'll want to let it hit the boss, at which point he will go into an AoE phase. Everyone should collapse on the boss. Use your defensive cooldowns to avoid his AoE damage, and your offensive cooldowns since he'll be vulnerable to more damage thanks to the ball. I have also had one or two raid groups ignore the ball altogether, which is possible in Raid Finder mode but will also mean the fight takes longer due to a smaller damage debuff.
Yor'sahj the unsleeping
The big issue with Yor'sahj is keeping track of which slimes he's spawning. Every so often during his fight, he will spawn a group of multicolored slimes. One of these slimes must die, because when the slimes reach him, they will give him some powerful buff. You will only have time to choose one slime, so choose well. It is always best to follow the raid leader's kill order so everyone's on the same page, but my preferred priority is to kill the purple slime, the yellow slime, then the green slime. That is, if purple's not up, kill yellow instead, and so on. You can remember this easily too, since the acronym is PYG, which sounds like the animal that provides everyone's favorite breakfast meats. If you're the tank, you'll be focused on the boss, of course, but as a DPSer you should be ready to break from the boss as soon as the slimes appear. Use your offensive cooldowns if you need to -- just kill that slime before it hits Yor'sahj.
Yor'sahj's slime buffs are pretty weak on Raid Finder, but there are a couple to worry about it. One of them will make him summon a Mana Void, which leeches mana. This won't directly affect us since we don't use mana, but if you're a DPSer, break from Yor'sahj and take it down. Your healers will thank you. Likewise, there's another possible slime buff that will summon a multitude of adds. When they appear, you will definitely want to go into AoE mode, using Howling Blast spam or Blood Boil and Death and Decay to deal with deal with them as appropriate. Also, some of the oozes will cause Yor'sahj to deal AoE damage. Use defensive cooldowns to mitigate as needed.
For the most part, tanks have this fight pretty easy. Just keep Yor'sahj occupied, and you should be fine. Use some AoE if you can when the Forgotten One adds show up.
Hagara the Stormbinder
Hagara is a pretty easy fight to tank. Just try to tank her off to one side if you can; that way, you'll have time to dodge her ice spikes when she runs to the center of the room to summon them. It's also worth noting that you can step backward from her Focused Assault. Otherwise, she's pretty easy on Raid Finder mode. As a melee player, you shouldn't have to worry too much until her ice and lightning phase.
For the Lightning Storm, she'll put lightning spires at the edge of the room, one of which will have an elemental guardian. Destroy that guardian, then begin running around the edges of the ring, generally in a clockwise direction. This is because in order to take down the spires, you need to make the lightning they emit chain between them. The lightning will jump from player to player, so if you spread out, they will eventually jump from one spire to another. You need to do this as quickly as possible, since the lightning does do damage, and that damage will eventually overwhelm your healers. Use your Anti-Magic Shell if you need to to mitigate a bit of it.
For the ice phase, you need to watch for the Ice Waves she sends out. These waves will turn into four walls of ice that will start rotating. If you are hit by a rotating ice wall, you will die. So in order to beat this phase, you need to run around the outer ring, dodging the ice walls and at the same time killing the four ice crystals she has set up. This can be difficult for us as melee players, for sure, since we can't get so fixated on killing a crystal we get caught in the ice wave behind us.
When you successfully defeat a lightning phase, Hagara will get a damage debuff for 15 seconds, so this is a good time to unload all your offensive cooldowns to do maximum damage.
Learn the ropes of endgame play with WoW Insider's DK 101 guide. Make yourself invaluable to your raid group with Mind Freeze and other interrupts, gear up with pre-heroic DPS gear or pre-heroic tank gear, and plot your path to tier 11/valor point DPS gear.