In World of Warcraft: Cataclysm, Guilds can now gain experience and level up to a maximum level of 25. Each level provides new benefits to the guild such as bonuses to honor, experience, and reputation gains. Your character will gain reputation with your guild as well. Gaining guild experience and reputation with your guild are done simultaneously in three ways:
1. Questing: Completing quests will grant you guild reputation, and guild experience. Higher level quests yield more reputation and experience.
2. Dungeon and Raid Bosses: You will earn guild reputation/XP for defeating dungeon bosses with 3 or more guild members total. Bringing a fourth or fifth guildie will yield extra XP and reputation. At least 8 guild members are necessary for a 10 man raid, and 20 for a 25 man raid.
3. Rated Battlegrounds: If your 10 player group contains at least 8 guild members, then you will earn guild reputation/XP from rated battlegrounds.
If you leave a guild you will permanently lose reputation with that guild after joining another guild. If you rejoin your old guild and don’t join another, your guild reputation will remain intact. Guild reputation is personal, whereas guild experience is shared throughout the guild. As you reach higher reputation levels you will unlock personal guild perks.
The maximum amount of guild experience that can be earned per day is 7,807,000. This amount counts for all guild members combined. The fastest way to level up a guild is through questing and organizing guild groups for dungeons and raids. Naturally, the larger the guild, the faster the daily cap will be reached.