From Halopedia, the Halo wiki
Players typically advance in level by consistently placing in the top three and drop in level by placing in the bottom three. However, several other factors also affect this, including comparison of the player's level compared to the others in the game , what specific place the player came in (1st place will level a player up faster than 3rd), and their Kill/Death spread (for slayer games). Originally the games had five players, but was soon increased to six. On September 16th 2008 Lone Wolves player count increased from six players to eight players. In the February 2009 Matchmaking Update, Lone Wolves was reduced back down to 6 players, as 8 players on a small map like Epitaph would deem players' K/D spread as low.
There are many achievements that can only be achieved on Ranked FFA playlists, such as Two for One and Killing Frenzy, and now Lone Wolves is the only remaining ranked FFA playlist, and the only Halo 3 playlist to get said Achievements. Mythic Brawl, Living Dead, and MLG FFA no longer are ranked FFA playlists.
Maps Played In Lone Wolves
Note: All maps have an equal chance of being selected.
Gametypes Played In Lone Wolves