Halo 3 campaign scoring...?

[Master_Chief]

I have been trying to get the campaign scoring achievments and i can never get the score i need...i have all the skulls...i play it on heroic. I was wondering what are the easiest skulls to use? Does anyone have any tips how i can get the right score...these are the last achievments i need.
If anyone wants to help me get them add there gamertag...
thanks

 

[Leah]

I got the achievements and I played on easy. I also only used a few skulls.