Dragon Age: Origins

Here's how you can get "Harrowmont's Ally" and "Bhelen's Ally" in one playthrough.

Note: I'm paranoid about closing storylines off too early, so I usually delay picking a side until the very last minute. So there might be a quicker way to do this, but this method definitely gives you a decision point where you'll only have to replay about two minutes of story in order to get both achievements. [Edit: Shinerbock88 verifies you can still choose one side or another before you start the Anvil of the Void and still do both outcomes, thanks! I'll keep the description of what I did just for informative purposes -- but you can skip two paragraphs if you want to.]

First of all, the setup: I basically played both sides as far as gaining their trust. I accepted the initial tasks from both houses, got both of Harrowmont's champions to fight again, and turned both of Harrowmont's allies into enemies for Bhelen. At that point Harrowmont's emissary got mad but I agreed to play double agent for him, and cleaned out dust town.

Now you should be in a position where you're still begrudgingly trusted by both factions, and they'll both try to get you to go find Branka in order to get her endorsement. You'll also be finding out that Bhelen's pretty much a tool, but that's beside the point.

Play through the entire Anvil of the Void storyline. Whether or not you choose Caradin or Branka, you'll be given the opportunity to have a crown made so that you can basically choose the next king. After you get the crown, SAVE the game. This is your decision point. Leaving the anvil room you'll be given the choice to fast travel directly to the council chamber, where a cutscene immediately plays.

For "Bhelen's Ally" declare that Branka or Caradin chose Bhelen to be the next king. Harrowmont will concede, and Bhelen will prove how much of a bastard he is by having him executed. After you wash the bad taste out of your mouth at having basically given this guy the keys to the kingdom, he'll promise to help you with troops, and the achievement will unlock.

If you haven't gotten "Harrowmont's Ally" at this point, just reload from your save and follow the instructions in that achievement guide.

Both "Harrowmont's Ally" and "Bhelen's Ally" are available in one play through with a careful save.

Leading up to your deep roads trek it doesnt matter who you run your errands for. You can complete Harrowmonts tasks or Bhelens, or even both (with careful dialog choices Im guessing). Just play however you see fit, head through the deep roads until you preserve or destroy the Anvil of the Void. SAVE HERE after youve received the paragon crown but before ou head back to Orzammars Council Chamber. When you do head to the Council Chamber a cut scene happens. Through a series of dialog options you can pick Harrowmont or Belen, even if you didnt help support them before you left for the deep roads.

Crown your King and reload your save. Do it all over again for the other achievement!

Once you return to the Orzammar Chamber of Assembly after the Anvil of the Void quest, you'll have to choose a new king for Orzammar. For this achievement, say that Branka or Caridin chose Bhelen to be king. After a conversation with Bhelen, you'll unlock the achievement.