This is really quit easy, and depending on how careful you are you can get four achievements at once. Three at the very least.
- Tsantsa
(Recommend finding all skulls first.)
- Walk it Off
(Note that you have to restart the mission if you accidentally pick up a health pack. Reverting to checkpoint doesn't work.)
- Overshields are for Sissies
(In the Covenant boarding ships. Don't touch.)
- He’s Unstoppable!
(Stay behind corners while things go Boom.)
Basically you only need the Boom, Bandanna, and Grunt Funeral skulls on. Obviously if you don't have a new copy of the game you can't use Grunt Funeral. But seeing how I posted this the day after launch, just about everyone should have the skull. As for the other skulls, check out the "Headhunter" achievement solution. People have been posting very useful YouTube videos showing the locations.
Anyway, aim for grunt head shots or throw a grenade around the corner and then hide while the Grunt Funeral and Boom work together to cascade the kills. Bandanna gives you infinite ammo and grenades, so no worries on running out. If an enemy hides around a corner, just keep chucking grenades until he is dispatched. As someone asked in the comments if co-op would be a good way of getting this achievement. Yes, co-op is always better. Just try having a friend available so you don't have to keep swapping controllers.
Updated - Nov. 18, 2011.