The daily experience cap for a guild is 7,807,000 XP. If you want to level up your World of Warcraft guild as quickly as possible, your goal will be to earn this much XP every day as a guild. Here's a list of activities that will contribute toward this daily goal of 7.8 million experience points:
Weekly Guild Challenges
Every week, your guild can complete a total of eleven guild challenges: 7 dungeon challenges, 3 rated battleground challenge, and 1 raid challenge. If enough guild members are in a group, completing a level-appropriate dungeon, winning a rated battleground, or taking down a raid boss will give credit for a guild challenge. It is wise to complete all 11 guild challenges every week, as the XP from these does not count toward your guild's day XP cap!
Quests, Quests, and More Quests!
Doing quests contributes to guild experience gain, and the higher level the quest, the more XP is earned. Tol Barad & Tol Barad Peninsula daily quests are perfect for this. Having several guildies do these quests every day will make it easier to reach your daily XP cap.
Dungeons and Raids
Any dungeon or raid boss that is defeated with enough guild members present will award guild XP. Even if it's low level – yes, you will earn guild XP for running your guildmates through lowbie dungeons and raids! This is a fun way to both earn guild achievements and level up your guild.
A rated battleground team with at least 8 members in the guild will provide XP when you win a battle. Guilds with a heavy PvP focus will find this is a great way to contribute XP to their daily cap.
Even Small Guilds Can Level Fast
Even if you can't get a rated battleground or raid team together, getting at least 3 people together for dungeons can provide a nice boost to your guild's leveling. Questing at max level is also a great way to get guild XP, especially when done in a group as it can be done rather quickly. Having a few active, high-level characters in your guild that frequently quest and run dungeons can help your guild level up very quickly!