First of all, each guild has a guild master (GM) [note: obviously not the same thing as a game master (also GM)]. The guild master can appoint people to different ranks in the guild, and recruit new members themselves. They are basically in charge [kind of a duh].
The next rank is Admin. These are some of the GM's trusted friends who have the ability to recruit new members as well. Usually when the GM is not logged on, or is gone for a while, the Admin or Admins are placed in charge.
Next is Council. They are closer to Admins, but do not have any recruiting abilities like the GM/Admins. They just show that the level of trust the GM has for you has gone up. It's a good thing
Next is Guard. These are ranked higher than Member, but are very similar to Council. They cannot recruit new members. Once the GM gets to know you and likes you, you will usually be appointed Guard.
The starting rank is Member. Once you join, you are (obviously) a Member. Members really do not have any special abilities whatsoever, but by putting yourself out there in the guild chat you could probably move up to Guard relatively quickly.
Now that the ranks have been explained, I'll try to answer some FAQ's, and just explain more about the process for getting accepted into a guild.
THE PROCESS Edit
FINDING A RECRUITING GUILD
If you are really dying to join a guild, the best way is to announce it. Using the Party Matching board as well as Shouting is a good way to get yourself noticed. When you do announce that you want to join a guild, it is REALLY important that you remember to give your info. Most guilds have a level limit, so the GMs and Admins do not want to waste time interviewing someone who is a lower level than they accept. Basically, you should include:
1. Your level
2. Your class
3. What type of guild you want (warring or not)
If you are shy about announcing to the world, you can always do some research yourself. Ask some of your friends if their guilds are recruiting, or check the Party Matching board and Shout periodically, since many guilds post when they are recruiting.
When you are looking for recruiting guilds, it is always important to remember to have COURTESY. Spamming/stalking their members will not get you any popularity votes. If a guild says no, then say "np" and walk away. Don't get offended if not every guild is willing to recruit you. There are plenty of guilds out there to join, more than enough for everyone. Also, if you join a guild, please do not bug the Admins to recruit all of your friends, or tell your friends you will recruit them. Most GMs/Admins like to interview or get to know the members they recruit. This brings us to....
"The interview" is not all as serious as it sounds (most of the time). Usually, if you find a guild that is recruiting, the GMs or Admins will want to talk to you. Don't get nervous, it's a normal thing. In fact, it's a really good thing because it means they are filling their guild up with people that are active and fun. The questions will probably go along the lines of "What is your info (class/lvl)", "Are you active", "Are you on daily", "Is this your main character, or is it an alty (alternate)", etc. Just answer honestly, and chances are it will go fine. Again, the Gms/Admins only do this because they want their guilds to be fun and full of interesting people. JUST BE YOURSELF Note: some guilds will NOT interview you, or get to know you beforehand. This is not necessarily a bad thing, but it also means they do not really screen the people they admit so it might not be as active of a guild as others.
WHAT TO LOOK FOR IN A RECRUITING GUILD Edit
Guilds are really all about personal preference. You can always quit a guild if you do not like it, and are free to join another after. However there are usually a few important things to look for in a guild. Note: Not all of these may apply to you, and that's ok. These are just a few things to think about.
1). Do they whisper/interview you before they recruit you?
As mentioned before, not all guilds interview you. Chances are, if they don't, they are either a) new and trying to get a lot of members; or b) just trying to get more members in general. Guilds that spam invites tend to be less active, and tend to talk less than other guilds. This is not always true, but when in doubt go with the guild that has an interest in who you are. If they happen to know you, and feel you are exempt from this, then this does not apply.
2). Are they a warring or fighting guild?
Many guilds that are very into warring or fighting will ask to see your killing skills before they recruit you. If you are really not into fighting, and more into partying and meeting friends, then you should ask about their affiliation. There are guilds that always war, guilds that sometimes war, and guilds that never war. None of these choices are bad, just based on a different personal preference.
3). What is the size of the guild?
For some people, guilds that are very large have a nice aspect. Others prefer smaller. Either way, you should ask the recruiting GM/Admin if the size is a deciding factor for you.
Does the guild talk frequently/get along well?
This may seem like an odd question, but it is much more enjoyable if your fellow guild members are very active and are willing to talk and party basically all the time. It can be very boring when no one is talking, so you probably want to pick a guild that gets along very well with each other so there is always an interesting conversation to stick yourself into .
After you join a guild, try to add your guild members as friends, and build relationships with them. They're not just a green title above your head, they're actual people that can turn out to be some of your very close friends .
WHEN IN A GUILD
Do as the guild members do....Basically, OVERUSE the guild chat, and feel free to talk to anyone even if they think you are weird . Getting to know people is a really good thing in a guild, because they will begin to trust you and you will move up in rank. Also, you make a ton of new friends who are willing to party with you if you add them to your friend list. DON'T BE SHY!!
LEAVING A GUILD Edit
If you are unhappy about anything in your guild, or simply wish to join another, it is possible to leave a guild.
1). Go to Community ('F' key), then "Guild"
2). Click "Menu" on the bottom right.
3). Press "Leave Guild"
Voila! You're out.