Instructions
Create your guild with an attractive name. All other things being equal, players will prefer a guild with a name that sounds intelligent and meaningful, such as "Ad Astra" or "Sanctum," to one with a name that doesn't, such as "LoL oMg BbQ."
Invite in-game friends and acquaintances to the guild. If necessary, create new characters, invite them to the guild and level them a bit. The purpose of this is to give the impression that the guild is active and has a fair amount of members, so players who join don't immediately leave.
Set up guild ranks so that all players can invite others to the guild. This allows leveling players to invite their friends and acquaintances to your guild, helping it to grow.
Purchase at least one guild bank tab and fill it with items useful to leveling players, such as low-level gear, potions and crafting materials. Ensure that all members have access to it, but limit item withdrawal to a maximum of one or two items per day to avoid people joining your guild, taking all the items from the guild bank and leaving.
Place some gold in the guild bank. Restrict gold withdrawal to yourself and the guild officers, but ensure all members have access to 10 or 20 gold's worth of equipment repairs every day. Most leveling players won't use this much, but they will appreciate it being available.
Earn some guild experience by questing and completing dungeons in a guild group. Doing this will give new members the impression that the guild is active. Additionally, the first seven dungeons you complete in a guild group will earn extra gold for the guild bank and grant additional guild experience. If at all possible, wait with recruiting players until the guild has reached level two and you have unlocked the first rank of the "Fast Track" perk.
Write an advertisement for your guild detailing all the benefits it offers. For example: "New leveling guild <Ad Astra> is looking for members! We have the 5% experience increase, free guild bank repairs and useful items in the guild bank and regularly run dungeon groups. Join now and invite your friends, too!"
Create two separate macros, one to send your message to the general chat channel and one to send your message to the trade chat channel. Click on the first macro periodically while you are traveling around the world, and click on the second macro periodically while you are in capital cities where the trade chat channel is available.
Advertise your guild in the Guild Finder tool, accessed by typing the "/guildfinder" command. Periodically check the tool and invite all players who have requested an invite, as well as any players you see listed in the tool who are looking for a leveling guild.
Install and use a guild recruitment add-on such as Guild Recruiter. These add-ons allow you to whisper all unguilded players within a zone with a short recruitment message and send them an invite to your guild.