For newcomers looking to get into League of Legends ranked play, the game's Elo rating system isn't as immediately straightforward as they might have hoped. With Season 3, Riot Games will be introducing a new system not unlike the ranking used for multiplayer in StarCraft II.
Put simply, players will compete to advance through six tiers, all of which are broken down into five divisions except for the final Challenger tier. Riot has a visual explanation of how the system works and what it'll take to become a pro in this infographic, as well as a more in-depth FAQ viewable by following the previous link.
The hope is that this overhauled system will "provide milestones and manageable goals you can strive to achieve at your skill level. Through leagues we can move away from focusing on a single number as the core indicator of a player’s skill, and instead move toward something more compelling: competition on a small ladder with a relatable number of opponents."