Boosting

'Boosting' is an illegitimate way to earn achievements. It is done by asking other people in your party in lone wolves to cooperate in getting achievements. Some examples:

Have a player stand in front of you and run them over with a mongoose for 'Mongoose Mowdown'

Have a player board your ghost, then board it back in 10 seconds for 'Maybe Next Time Buddy'

Have a bunch of players stand in one straight line and blast through all of them with the Spartan Laser for the 'Overkill' and 'Two For One' achievements.

Boosting is an easy way to get that Katana Chest Plate or Security Helm you wanted. However, i do NOT support boosting in ANY WAY AT ALL. But if you just cant seem to get the achievements, then you can try this as a last resort.

Hope this helps.