When you start on the beginning of the level move towards were you need to go. there is a AA rocket platform. the building be hind that has a lone flood that will jump across the street to the other building shoot it just before it jumps and the skull should fall. it may take a few tries.
the fog skull takes away your radar. you find the skull on floodgate
Floodgate
Tsavo highway and Floodgate
Chieftains are one all the levels except floodgate, Cortana, and Halo.
If by parasites you mean the spores on the levels floodgate,cortana and halo no they do not count as kills so sorry.
No
The first skull on halo 3 is a silver skull. Silver skulls do not award any achievements.
After finding a halo 3 skull, simply pick it up as you would any other weapon.
Well the Fog skull is on the level Floodgate. When you are walking towards the first battle you'll hear Flood roaring. Take note of the Flood jumping across the roofs. Use a Battle Rifle to kill the Human form when its in the air. The guy will drop the skull.
once you get a skull in halo 3 you can co to the campain options and turn it on different skulls do different things
13
http://www.halo3planet.com/halo-3-skull-locations/ is were I found them