I do key runs at the highest MP I'm capable of without dying too often. By too often I mean once every couple runs or if you make a mistake, run face first into RD packs.
**If anyone has input on a possible faster way, please share, I'm always looking to shave some time off of a run**
This guide was made with the WW build in mind. For other builds, this may not be quite as efficient, and some tips posted below will help you better.
Act I, Key of Destruction
I pick the last quest
WP to Festering Woods, run around some, there are usually 2 elites wandering around outside the tombs, and sometimes an event to complete. (these events take a bit longer than killing an elite pack, so its your call if you choose to do it or not) Kill them and clear the tombs, 3-5 stacks. I TP and go to the Fields, 3 or 4 stacked, and start looking for the warden, you generally run into a pack or two searching. If not, TP out and go to the cemetery to fill your stacks.
The cemetery is another place to start your 5 stack quest, though I find it slower than Festering Woods, there are some really easy events to complete.
The jar of souls event, located in the middle of a random crypt, just activate the quest, leave the room, search the rest of the dungeon, and pop back in to smash the jar. Quest complete, no time wasted killing monsters for 30 seconds.
The other quest, the one with the female ghost, requires you to activate the urns. Just hit all three urns, click on the tomb, quest complete, no need to deal with skeles :D
**Something to know about the crypts, there is never more than two elite packs in any given crypt, if you kill two packs, TP out and restart with another crypt.**
Act II, Key of Hate
I pick the black soulstone quest
While there are a couple different ways to complete this run in decent time, I've found it best to go right to Dalgur Oasis and look for the warden. There are quite a few elites usually, and some scattered events. One of these events, usually spawns near the WP, or the CP "The Forgotten Ruins" will give you 5 stacks right there. Heres a pic of what it looks like on your map:
Its the Khan Dakkob (or something simiilar) quest. There is an elite, around or inside this ruin, one elite when you activate one of the two levers to open the tomb, 2-4 elites inside the tomb, and the event. Quite an easy and fast way to get 5 stacks, and its really close quarters. Even if you dont find this tomb, I find it efficient to locate the warden, killing elites along the way, then TP out of there to town, SAVING THAT TP FOR A FAST RELOCATE, TP to Black canyon mines and clear. If needed, use the WP to travel to Road to Alcarnus to fill your five stacks, then use the WP to go back to town and TP to the warden. Every once in a great while, you may get shafted and need to visit the sewers to get your 5th stack, thats only happened to me once outta hundreds of runs.
Act III, Key of Terror
I start the kill Azmo quest
This ones pretty easy, TP to Stonefort, run the battlements backwards, you should get at least 4 stacks. Then TP back to Stonefort and move forward. If the warden is at the beginning of Stonefort, and your not 5 stacked, use the WP to travel to either The Core, or Arreat crater 2. (Two places I consider to have elites close to the WP)
Thats about that, Hope this helps some of y'all farm a bit faster for those HF rings :D