There are good and bad ways to ask people to join a guild. While many people opt to only invite people who have partied with them, some choose to shout for guilds. The former seems like the only viable option, but the only problem with it is, if you are forming a special guild, such as a crafters guild, it will take you a long time to fill it up, as there will only be so many people that you meet who will want to join that. While you are trying to fill up the guild, others may leave since there are not enough people. So a way to find those people who's goals best match with the goals of your guild, is to advertise. Many people are very turned off from this method, because all they see are requests like this:

LarryLeader: Taking new recruits for Black Ice guild! PST is you are interested! (all guild names are made up)

What does this tell you? The name, yes. So basically, it tells you nothing. Do these bother me? No, not as long as they are not spamming.
But there are some things you can do to make this proccess easier for you, with much better responses.

First, you need to give any requirements for the guild

Keep it short and sweet. It will save time for you, and everyone else if you clearly put in any limiting requirements. Dont say: "OK, you need to be level 20 at least, unless you are an engineer, or a blacksmith, then you can be level 15 or so. If you are into mining, and can contribute ores to the guild, you could be around level 12 or so, maybe up to 14, depending on your minging skill". This is just a waste of time and space. In the case where these really are your requirements, then something like "Level 20 prefered, but negotiable"
will do fine, and work with people on a one-on-one basis, since it sounds like you are actually pretty flexible.

Sometimes, if you dont list requirements, people may think there are none, but not always. Say for instance, you are recruiting for a PvP guild. A level 13 player will probably not try to join because they would think that you want any low levels, since PvP is generally a mid to high level engagement. But what if you are willing to take any level, and help them to grow to be strong PvPers at higher levels?
Best to say if you have no requirements to join.

Second, what kind of guild is it

Every guild will fall into one type or another. Even if all you want is to have people to talk to and ask questions, then it is a social guild. Want to have buddies to help watch your back, and you watch their back on a PvP server? PvP Guild. Plan on tackling a lot of the Raid content that is coming to the game? Raid guild. Want to have other people to help with dependacies in crafting (when you need something crafted that you cannot make)? Crafting guild. Want to have a group of people who just level and level, to reach the higher-end content? Power leveling guild. The list goes on and on.

One of the best ways to determine what kind of guild you are going to make, is to stop and think about why you are making a guild. What do you want out of it? When you are positive you have determines what you want out of starting a guild, then that will most likely be what kind of guild it is.

If you do not list what kind of guild it is, then what you will usually get it just a huge group of people who dont talk. Everyone's goals are different, so there is not a whole lot of partying amongst the members. People will jump ship as soon as they come across a guild that is even slightly more geared to what they want out of the game.

List goals of the guild

Now this may be more of what you will tell people who respond then what you would chat to get people interested. Goals are as varied as guild types, and usually go hand-in-hand. Most people who are serious about a guild will want to know more about the guild's goals, so it is a good idea to be ready to provide this info.

Examples

Good:

"Crafting guild looking for lvl expert+ crafters, all proffesions PST "

"Raid guild looking lvl 50+ players. Proffesion required. PSt if interested"

"PST if interested in joining social guild for good conversation. No requirements"

Bad:

"Dragons of Archemgon guild looking for more members PST" - no info

"Guild looking for level 30+ members PST" - what kind of guild is it?
It could be Social or it could be Raid, and there is a world of difference between those two types.


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I know some people will say that it is a bad idea to just yell for guild members. If you do not list any info to help filter out all the wrong people for your guild, then it is a bad idea. If you just shout that you are taking recruits to a guild, then what you will get are mostly people who just want to be in a guild to "be in a guild". These people may just be tired of having people corpse camp them, and want to have an armada to call onto the offenders. This is not going to happen, unless their is a sense of camradery between them. And this camradery only comes from working towards goals together.

You can look at recruiting members this way as being like a pick-up group. You can sometimes get some bad apples, but if you discuss ahead of time where everyone is going, and what they are doing, it can be a beautiful thing.

Interviewing

When someone is interested in the guild, and would like to join, I highly suggest talking to them first. I dont suggest sitting them down for 30 minutes, talking to them about what games they have played in the past, references etc, but rather, just take a few minutes to talk to them. You may be able to see that they have a very bad attitude right from the start, whereas they may have run off some of your very good members off had they been granted immediate access. Like I mentioned before, this can be a good time to talk about their personal goals vs guild goals. See if these goals mesh. If they have mentioned that their primary goal is what the main goal of the guild is, and they seem to have a good attitude, they may sound like a winner.

Sometimes, if you aim to have a larger guild, you may need to grant others with the ability to recruit new members. You should speak with these people often about the current state of the guild, what is needed in the guild, and the current interviewing proccess. Make sure you trust the people that you are offering recruitment abilities to.

Tabard

I suggest getting a Tabard as soon as possible for your guild. It is nice that Blizzard included this, as things such as these, which show your guild insignia, are a great way to bolster guild pride, and make people feel as though they are a part of something. If people feel that they are part of something, they are more likely to make contributions to the guild, in the way of their time and effort. It makes people see themselves as part of a whole, working for a common goal.