A tank helping out their healer can go a long way. It makes people want to run with you, and you will make new healer friends that invite you along to their runs. This goes for guild healers as well as pug healers.
One of the easiest things a tank can do to help is use his cooldowns. In the AOE fest that was the end of BC, people stopped using common sense and cooldowns. Now that we are back to heroics and raiding, this can be bad. There are a number of things you can do to help your healing brothers and sisters out.
1) Use your trinkets: If you have trinkets with on use abilities, they should be on your tool bar. Better yet, make a macro that charges, then uses one of your trinket uses. This gives the healer a moment to get his bearings straight and start healing you. If you don't have on-use trinkets equipped (like me atm), then disregard this.
2) Mark targets for CC: It is not old and outdated. It is still good practice, and hit keeps you from taking 15k damage in a second. Marking has been around forever. Once again, people forgot about it in BC-AOE. Marking targets is also important as it make you learn what each mob does. Knowing your shit is part of being a good tank, and not a face roller.
3) Use your cooldowns: Pre Wrath, you didnt really need to use your cooldowns or special abilities. Shield wall was on a very long timer, and it was usually a given that shield block would be up all the time. Well, times have changed. Shield block is now on a 45 second cooldown. This is a huge change as you can no longer spam it. It is best used when pulling, then charging into a group. You take a lot less damage and give your healer a chance to catch up. Shield wall is now 5 minute cooldown and reduces all damage by 60 percent. Pretty nifty as it can be used on EVERY boss fight. Last stand is another nice OH SHIT button with pretty short cooldown. A new one is Frenzied Regeneration. This is basically a pretty powerful warrior hot that can help out a lot. If you notice you are taking alot of damage, it would be very useful help to the healer for you to pop it. It has a 3 minute cooldown.
4) Silence, and Stun, and reflect OH MY!!!!: These are normal abilities that should be used on a regular basis to help out your healer. Pretty much every tank should be specced into Gag Order. If you are, this gives you two silences. Heroic throw will silence casters as will shield bash. This is win. You can pull caster mobs with Heroic throw and have then run straight to you without having to LOS. Make sure that you are silencing caster mobs when you can. Spell reflect is also a very nice ability. If you are specced into the improved version, then you can reflect spells cast at your buddies as well. They will tank you for it.
5) Communicate: It is all well and good to use the abilities given to you. The last thing you can do to help out a healer is to let them know that you are popping a powerful ability. This may give them a chance to regen a little mana, or heal up an injured party member. In all relationships, communication is key. This includes the Tank-Healer relationship.
On a side note, I tried to mostly pug heroic VH last night, and it was not happening. I had a terrible DK for my guild who was doing under 1k dps, a pug hunter who was all kinds of dumb doing around 1k, and a very good pug hunter doing about 2k dps. The healer was also very good and a pug. Unfortunately, we got the Ethereal boss that drops the orbs, and the DPS kept doing dumb shit. The boss will enrage if his orbs get to close and hit me for 10-12k damage. Well, I would be kiting him along, and then all of a sudden, a bunch of ghould pop up and TAUNT the boss. He stays there whacking ghouls, the orbs catch up, he come back after me, and smashes me to bits.
We wiped 4 times on that boss before I logged off in disgust. I am probably going to talk to some officers about the DK, before he gets into a raid and sucks it up. During BC, he was an extremly well geared shadow priest that struggled to do 800 DPS. Now he is a level 80 DK and was only doing 800 DPS. He is well below the curve for similar geared DKs, and I fear he doesnt really know how to play. His terrible DPS was always tolerated because a) everyone likes him (he is a very nice guy), and b) he was a SP which gave mana to everyone. Now he is a DK which are a dime a dozen, and he really doesnt stack up.