Mission: Sierra 117
Effect: "Death carries a heavy price..." -- Instead of only losing 25 points when you die, you lose 75. You also restart from the beginning instead of any checkpoint.

After Freeing Johnson and killing all the covenent that come in the phantoms, walk to the Pelican that comes to pick you up. Face the cargo bay but instead of hopping in, turn left and follow the path. Once you hit the wall jump up to your right, eventually reaching a walkway. Walk all the way to the end, take a left, then a right, then at the end of this little bit to the right is a dark corner. Turn your light on and you should see the skull. If you cant see it you're probably standing on it.

Mission: Crow's Nest
Effect: "Bash your way to better health." -- Your shield will not auto-recharge anymore, you have to kill an enemy with a melee attack.

From the start without moving anything you can see a massive pipe above you. Walk up the stairs then up the next set, turn to your left and jump up on the shelf unit. From there jump to the red cross beam then up onto the pipe, from there just walk to the end and walk over the Black Eye skull to claim it. You don't have to pick this one up it does it automatically.

Mission: Tsavo Highway
Effect: "Your foes always make every saving throw." -- Enemies seem to avoid rockets and grenades easily.

After you have to deactivate a shield that's blocking the road, you will exit onto a bridge and a giant covenant ship flies overhead. You need to get out of your jeep if you are in one and go to the right side of the bridge, then go underneath and you will see bridge supports jutting out into the canyon. Jump onto the one farthest to the left and go to the edge and turn left and you'll see a small jut out of the cliff with the skull on it.

You get 1 EXP point if your team wins in a team game (or if your team is in the top 2 teams in a multi-team game) and you get 1 EXP point if you are in the top half of a FFA match (5 players, top 3 get a point). You can earn points in both Ranked and Social matches. You will lose EXP if you quit out of a team match, so avoid that.

For this achievement, simply get 5 EXP or finish 10 games. You can lose all 10 and still get this achievement.

Since the 25th of September 2008 the requirements for this achievement have changed.

To unlock this achievement you now need to reach 50 experience in any playlist, to earn the Lieutenant rank. 

This will also unlock the “Vidmaster Challenge: Lightswitch” achievement.

Your best bet for this is a King of the Hill game, seeing as everyone will be running into the same area. Hang back away from the hill and fire into it while people are vying for control. Not an easy thing to do, but keep at it. Best done at lower ranks.

Maps: Construct, Snowbound, High Ground

This must be done in the "Lone Wolves" game type.

This is best done in a King of the Hill or Oddball match, seeing as everyone will be running to the same area. Try to get a sword (this will get you the "Steppin Razor" achievement as well) or a rocket launcher. Otherwise, just get off some good grenades against people already battling and finish them off with whatever weapon you have equipped.

Maps: Any map, just takes skill and a little luck.

This must be done in the "Lone Wolves" game type.

See "Triple Kill" for tips. This one is decidedly harder since it requires you to kill all four of your opponents, but it does use the same principles.

This must be done in the "Lone Wolves" game type.

You have to get 5 total in a single match. Try to hang back away from people fighting and throw grenades in at them, or if you know someone has a sword, entice them to come after you and they should be lined up for an easy throw. The stick counts even if they die after you are already dead.

Maps: Guardian is by far the easiest.

This must be done in the "Lone Wolves" game type.

In the campaign on Tsavo Highway, shortly after the second chapter begins, there is a long building to the left that has Trip Mines in it. Grab one of these and proceed to the next area. Here there are Brute Choppers trying to kill you. You will need to attack the front end of the vehicle for a bit until about two small pieces fly off. Once this happens, it should be weak enough to kill with the mine, so place it down and step behind it, waiting for the guy to try and splatter you. It may take a few tries, but just reload the last checkpoint if you fail.

I don't want to embed it, because it's quite long (7+ mins), but this video shows where and how to attempt this: (youtube.com/watch?v=APgk132oGPg)

This one is somewhat difficult, but it can also be quite easy depending on your strengths and the skill of your opponents. If you're a good sniper, grab that and hide, only popping out to kill someone and moving spots whenever you shoot. Getting the sword or rocket launcher is always a good idea.

The way I got this: On Snowbound, grab the Spartan Laser and then hop in the ghost. Aside from the Brute Shot and Plasma Grenades, the enemies now have little defense against you. Keep circling the map and splatter or shoot anyone and use your boost to run away if you're getting hurt. I went 14-0 with this method. Lost the match obviously, but got the achievement.

This must be done in the "Lone Wolves" game type.

See "Triple Kill" for tips.

Maps: The Pit, Construct

This must be done in the "Lone Wolves" game type.

This one is tricky. You will have to hit someone with low shields and at high speend for it to kill them, plus you have no weapons while on the Mongoose to defend yourself. Your best bet is to find two people fighting and barge in, hoping they don't notice you and you can get one of them square on.

Maps: High Ground, Isolation

This must be done in the "Lone Wolves" game type.

Most of the battles in this game come down to an assault rifle spray and a beatdown, so this will most likely be your first online achievement. Sneaking behind people while cloaked will help as well.

This must be done in the "Lone Wolves" game type.

The meta-game is an overall score of how you do during a campaign mission. This thread on our forums has the scoring information, so check there for tips on how to get the required score for each level. Playing on harder difficulties, turning on skull and finishing quickly all give large multipliers to your score.

The "Bungie recommended" method is playing on Heroic with 1-2 skulls on. I personally did these on Normal with the skulls Fog, Catch and Tough Luck.

Get five kills with the gravity hammer. Unlike the above two achievements, it DOES NOT have to be a spree. Must be done on Assembly.

(Mythic Map Pack)

Like Blades of Fury, you need to get a killing spree... with a shotgun. Must be done on Citadel.

(Mythic Map Pack)

You need to kill five players with the sword IN A ROW. This can be made easier if you use active camo and must be done on Heretic.

(Mythic Map Pack)

Splatter or use the plasma weapon on the ghost and kill three people. This should be very easy if you know the basics of how to shoot and drive. Must be done on Longshore.

(Mythic Map Pack)

Get in the habit of throwing grenades. Lots of them! You have to kill someone after your dead. Another way of getting this without using grenades is by using a weapon that travels slowly or over a long distance (such as the rocket launcher of needler). With some luck, you should get this in no time. Plasma grenade stickies just before death are a very easy way to get this, but note that sometimes they won't count as Death from the Grave kills.

(Mythic Map Pack)

To get this, you have to kill another player who is in the middle of a sword lunge. You should use the shotgun and melee combo against a player.

(Mythic Map Pack)

One of the easier achievements to get. Just randomly kill people and at some stage in the match someone will have a killing spree.

(Mythic Map Pack)

The Killtacular medal is one step further when compared to the Overkill achievement. This requires that you get 5 kills in any match. However, this is substantially easier than Overkill because it CAN be done in social matches. Should be done in Grifball. Your opponents have a respawn time of three seconds instead of four, so you can spawncamp them and the kills will count towards your multikill.

(Mythic Map Pack)

The Extermination medal is awarded for wiping out the entire team with at least an Overkill. Very easy to do on Grifball, as multikills and exterminations are extremely easy to achieve.

(Mythic Map Pack)

The Perfection medal is awarded for winning a slayer game by more than 15 kills without dying or betraying someone. This should be boosted by a party as it is quite hard to get in ranked or competitive social. Try to stay back and let your teammates do the work, and occasionally popping out to finish off someone else's kill.

(Mythic Map Pack)

Like Zombie Repeller, just the opposite. You have to be the zombie in an Infection match and kill two humans (the non-infected players). Try and get active camo, as it will make it a lot harder for humans to detect you.

(Mythic Map Pack)

In an Infection match, kill two zombies. Easiest done on the Braaaains gametype, as zombies have no shields, making it one hit kill with the shotgun or two bullets with the Magnum.

(Mythic Map Pack)

While in Forge, go into monitor mode and spawn any vehicle. Get another player to stand still (preferably) and swing the vehicle from side to side at his position until you splatter him/her.

(Mythic Map Pack)

See the "Sandbox Skull" achievement for more details.

(Mythic Map Pack)

See the "Sandbox Skull" achievement for more details.

(Mythic Map Pack)

Thanks to Maka for creating the video. Ideally, open the page up and take a look at the description, watch in higher quality, etc. There is a premade map for the Sandbox skull.

(Mythic Map Pack)