Skill

Skill is awarded to players of Halo 3’s Matchmaking, along with experience points. This can only be obtained on ranked playlists, such as Lone Wolves or Team Slayer.

Gaining Skill
There is no set process to gain skill, but that your skill is akin and relative to other players currently playing Halo 3 in Matchmaking. You do not gain skill unless you become appreciably and significantly better. If you develop a greater headshot ability, your skill level should rise noticeably, unlike with EXP, which only changes if you win a match. Though skill is earned much quicker by winning free for all games, than by playing team games.

Skill Guide

 * 1-10: Lone Wolves - All you have to do is get in the top 3 and you get exp, and it goes towards a skill point, a lot of people who play lone wolves suck so it isn't too hard
 * 10-20: Lone wolves/Team Slayer - Lone Wolves, once again, quite easy to advance up until about skill 25 area where you start getting headshotted without even knowing where you just spawned. Team slayer is also good if you have a group of friends you can play with, making sure you stay in contact with eachother via headsets is the key.
 * 30-40: I dunno i'm not there yet, someone else can add this part.
 * 40-50: What did i just say?

Complications
However, there are complications to getting up the ranks:
 * One is that when you have played a lot of matches, the game will be able to work out what your "win:loss" or "kill:death" ratio is, and if you start to change the percentage, this will help you go up the ladder and ranking scheme, but if it stays the same, it can make this very difficult.
 * As it has been told time after time again the hardest way to rank up is in Ranked Big Team Battle's as it is a 50/50 gamble when you enter the pregame.

Skill and Experience
Skill level and experience are measured in the Matchmaking system. Players will be rewarded with experience Rating Points (RP) earned for winning a game in Halo 3 Matchmaking. Progress from recruit to officer is a reward for many wins and another way for games to be evenly matched.

Experience Rating Points and their associated rank status (Sergeant, for example) will give other players an instant feel for how long you’ve been playing and how that compares to your relative skill level in a given playlist. A player with many RPs and a low Matchmaking skill level might be new to that specific matchmaking playlist. Knowing that is the key to knowing an enemy or teammate.