If you are going to power level yourself with a high level in instances this is the fastest way.

Make your character and hand level it 1-8. Once you have all the characters you wish to powerlevel run them as a group to Orgrimmar and park them in front of Rage Fire Chasm.

A paladin is the best class to use, the gear does not need to be spectacular but the better the gear the better you will do. If you have excess money laying around I would suggest buying Earthen Elixirs (These will be used at a later level).

The Paladin should be spec'd protection for maximum efficiency. You will want blessing of sanctuary. If you have sporegar rep get yourself the honored rep shield from there, each time you block you proc a dot that does 12 damage and stacks 5 times, throw a shield spike on that bad boy.

Your method is going to be to use the paladin to kite as much of the instance in one pull to your newbies as is possible and then kill it all off. A few tips that will help you if you do not have or do not play a paladin regularly. Learn to strafe run, this entails running sideways at all times while still moving forwards, this will present your shield to a good number of the guys chasing you allowing you to cut down the damage you take. Alternatively you can constantly jump and do 180 or 360 degree turns. When you do this you want to spend as much time airborne facing backwards as possible then flick forwards so you can continue to jump. Always keep Blessing of Sanctuary up, alternate between seal of light and seal of wisdom at need.

Now for the locations and my recommendation on pulling.

8-15 Rage Fire Chasm. This has to be a two pull. There are two distinct areas of the instance, the first area is made up of troggs, these guys are candy and you will quickly wish the entire instance was made up of troggs. Collect them all up, including the ones that are off to the side of the ramp and kite them back to the zone entrance. AoE them all down. Put your newbies on follow and take them to the ramp up to the Orc area. About halfway up this ramp you can leave the newbies behind as it will be safer for them there. Now you can go collect all the orcs, the orcs however will knock you down and as the pull gets larger it is possible to get stuck in a knock down chain that makes it difficult to move. The route I would suggest is to bare to the right while collecting the orcs. You will head up to the satyr and then you should drop down below. Heal if you need it and then run out collecting up the rest as you go. Take them as far as you need to so that your newbies are just below you on the ramp. Kill them and then go reset the instance.

15-20 Shadow Fang Keep. This overall is much easier than RFC and the knock down happy orcs. You will have to clear to the door so that you can unlock it so do that. Now move your newbies up to that doorway and leave them inside it just above the stairs that head down to the courtyard. If you have an under geared paladin you may wish to do the remainder of the instance in 2 pulls as it will entails a little but of doubling back. I did it in two pulls but I probably could have managed 1, I however didn't want to risk death and the time setback so I played it safe. There are two paths to take once you gather up the initial courtyard. One path that goes to the right past the butcher and then the path through the kitchen to the butcher. I would take the right path and gather everything as I made my way to just before the bats and Odo (I believe his name is). I would kill this group right here and then jump down onto the ramp right by where the newbies were. I would then make my way through the kitchen and all the way up to the big wolf Fenris. In that spiral ramp just outside of his room you are again close enough to your newbies that you can kill here and they will get the XP. I didn't bother with the rest of the instance.

20-40 Scarlet Monastery. The pulls here are a no brainer, you will be doing all of the Armory in one pull and Cathedral will depend on you having the figurine of the colossus.

Catherdral single pull- If you have the figurine you can pull the entire instance in one go. The method I would recommend is to pull one side of the instance on your way up, divine shield at the door, open it and then agro Mograine. He will trigger the entire Cathedral part of the instance, now you kite your way back down the left side. I would recommend that you jump off the fountain and tossing yourself a heal before you gather up the rest of the instance. Once you are in the entrance tunnel you can stand in the window sills to break line of sight to casters to force them to all bunch up on you. Pop figurine if you need it.

Cathedral two pull - If you do not have a figurine I would recommend you do it in two pulls but you may have the gear anyways to manage it in one. If this is so then refer to the above paragraph. If you decide on two pulling again use the same technique as mentioned in the above paragraph only skip opening the door and pulling Mograine. Clear everything outside, then do inside on a seperate pull, be sure to collect anything you may have missed first time around to maximize your XP.

I am currently at level 41 with my 2 replacement shamans at 20 hours played. It was a learning process for me as I haven't played this old paladin of mine in about a year and as such it can be done faster.

45-55/60 I intend to do strath for this. You will only want to do the undead packs and then reset.

It is possible to hit 60 in less than 2 days played power leveling in this manner. If I wasn't lazy i'd diagram the pulls but I am lazy so you are SOL.