A boosting lobby is either in Team Tactical or Free for all (Team Tactical is better). You will have a partner and you and your partner decide who gets head-shots first and how many you get. You will usually discuss who gets nuke first if the host wants people to get nukes. (usually allowed)
If you would like to host one then you need to find 7 more players and then get all of you in a Xbox Live Party Chat then you will split the players in half.(make sure you don't put partners on the same team) Make sure one person is already in the party menu and awaiting for your signal to send the invite. You then start the game, you tell the person to send the invites then you can send one to a individual if you would like to because if one person join then it stops the process of searching for other players. Make sure the game mode isn't Search and Destroy or Team Deathmatch and if it's TDM then just make everyone get 12 kills then you divide the rest of the kills up. (50 kills win TDM in Team Tactical)