halo 3 meta campaign achievements

at the moment i am trying to get the meta-campaign achievements for halo 3 but i am finding it difficult. it may seem stupid to some of you that i cant do them but i really need some help or tips. thank you

xbox360achievements.org, probably the best place for achievement help. I can't remember 100% exactly what you needed to turn on (skull wise), but I followed the guide on there and it was really easy to get those achievements.

yeah activate the skulls(not all of em! lol), get plasma pistol+br kills on brutes for extra points. be patient, get needler, idk anything to help ya.gow117