If you want two protectors on a vehicle get a Spartan and a vehicle and place a protector on each. Then have the Spartan take over the vehicle and you will now have two protectors for your Spartan/vehicle.
On each mission complete the task and then search the indicated location to find the corresponding skull. When you have the skull you will be able to activate it's special effect at the 'Pause' men. Collecting the skulls is also a requirement for the 'Alas, Poor Andrew Thomas' and 'Graverobber' achievements.
Mission 1 Skull - Alpha Base: Kill 100 Grunts. The skull appears east of the entrance to Alpha Base.
Mission 2 Skull - Relic Approach (Look Daddy!): Kill 20 Jackals. The skull appears at the bottom of your base.
Mission 3 Skull - Relic Interior (Grunt Birthday Party): Kill 45 Hunters. The skull appears where you rescue Anders and the Marines.
Mission 4 Skull - Arcadia City (Wuv Woo): Kill 50 Elites. The skull appears south of the Covenant base on the east side of the map.
Mission 5 Skull - Arcadia Outskirts (Fog): Kill 5 Wraiths. The skull appears at the northern-most part of the highway on the west side of the map.
Mission 6 Skull - Dome of Light (Sickness): Kill 50 Banshees. The skull appears on the small platform where you lock down the third Rhino.
Mission 7 Skull - Scarab (Rebel Sympathizer): Kill 10 Locusts. The skull appears by the northeastern most power node.
Mission 8 Skull - Anders' Signal (Rebel Supporter): Kill 750 Infection Forms. The skull appears north of where you set up base.
Mission 9 Skull - The Flood (Rebel Leader): Kill 20 Flood Stalks. The skull appears just east of your base, near a downed Pelican.
Mission 10 Skull - Shield World (Catch): Kill 350 Swarms. The skull appears on a small island between the southern Pylons (need an air unit).
Mission 11 Skull - Cleansing (Sugar Cookies): Kill 100 Sentinels. The skull appears at the back end of the ship where the cleansing shields start (air unit is required).
Mission 12 Skull - Repairs (Boomstick): Kill 12 Spirit Transports. The skull appears near the back of the ship, just above the two interlocks (air unit is required).
Mission 13 Skull - Beachhead (Beachhead): Kill 10 Bomber Forms. The skull appears in the small valley west of where you start the level.
Mission 14 Skull - Reactor (Bountiful Harvest): Kill 20 Vampires. The skull appears at the bottom of the third ramp between the second Covenant base and the wall of the mountain.
Mission 15 Skull - Escape (Emperor): Kill 3 Scarabs. The skull appears in the middle of the north part of the map in the middle of the Flood.
Search the following locations to find the corresponding hidden Black Box to unlock new Halo History entries which are needed to get the 100% achievement. Black Boxes can also be unlocked by winning different Skirmish matches with each leader.
Black Box 01 - Alpha Base: Under the last bridge before entering Alpha Base.
Black Box 02 - Relic: Approach top left of the map, behind a Covenant shield.
Black Box 03 -Relic Interior: On the small ramp on the left side right at the start, before going inside the Relic.
Black Box 04 - Arcadia City: Just north of the starting point, right next to the skyscraper where you can save Adam.
Black Box 05 - Arcadia Outskirts: Go down the first ramp as you are fleeing from the Covenant, it's behind a downed Pelican.
Black Box 06 - Dome of Light: Far left of the map, to the left of where you transport the third Rhino tank.
Black Box 07 - Scarab: Far right side of the map, in a small alcove with supply crates.
Black Box 08 - Ander' Signal: Near the big brute fire line at the start, on a ridge to the right.
Black Box 09 - The Flood: Straight out from the base ramp on the other side of the map.
Black Box 10 - Shield World: Alongside Bravo platoon, which is the middle platoon you pick up.
Black Box 11 - Cleansing: Left rear of the ship, on wings that slant down (requires a flying unit).
Black Box 12 - Repairs: Left edge of Spirit of Fire, not far from the Power Core building, on the left side
Black Box 13 - Beachhead: On a ledge near the second set of teleporters, near the Covenant base.
Black Box 14 - Reactor: Up and to the left at the peak of first ramp. It is on the edge of the ramp.
Black Box 15 - Escape: Directly opposite the starting point on the north edge of the map, between the Flood and the Covenant base.