When to join a guild

Overview
There are several points you have to keep in mind when considering to join a guild, especially if you are a lower level character. There are factors such as number of members, alliances, guild halls, kindness of members and farming. Although these are just a few of the things to consider, those are the main points. There will also be a miscellaneous section where some other factors will be touched upon.

Number of members
The number of members in a guild is important to your selection in many ways. If you like farming, a high-member guild would best suit you, so you have a better chance of getting people to come farm with you. If you want to be an officer, a lower-member guild gives you a better chance of being one. Some guilds will offer you an item or sometimes money to join. Be cautious, and ask about the number of members, what kind of guild (farming, GvG, High-end PvP, High-end PvE, etc.) it is. If you are looking for a guild with a lot of members, your best chances lie with an active PvE guild. Often said that PvP guilds have more members, but the fact they need members for standard teams and just a few replacements, means they do not have a lot of members.

Alliances
Some guilds are part of what's called an alliance (several guilds formed into a group with one guild as the leader). This allows alliance chat, which allows you to talk to other members of an alliance without using the "all" button. A guild that's part of an alliance can take part in Alliance Battles, in which guild members fight other players that are part of an alliance. If you want that, then join a guild with an alliance. Another plus is meeting more members that are willing to help you. An alliance can have two Alignments: Kurzick or Luxon. Make sure that you want to join the Alignment of the alliance. Also keep in mind, that some guilds want you to donate a specific amount of Luxon/Kurzick faction each day/week/month.

Guild Halls
Guilds with Guild Halls are helpful because of what they have in them. From there on you can go to Kurzick or Luxon battles, add henchmen (for a GvG or scrimmage) and sometimes there will be merchants selling weapons, armor, crafting materials, dye, runes and more. These need to be bought at the Guild Lord. Also, if the guild is part of an alliance, you can visit their Guild Halls if yours doesn't have the required merchant.

Kindness of members
Joining a guild with "bad members" can hurt your chances of GvG, getting help, or just having fun. Guilds with friendly members will (relatively) help you more with quests, missions, capping elite skills, or getting a better item. Also, talking with them while playing can be stress-relieving.

Farming
Some guilds are called farming guilds, guilds whose members come together at a certain location and kill one type of monster there for a specific item or amount of gold. Farming guilds can help you earn money as well as getting experience to level up. Most farming guilds have friendly members, so aiming for one of those guilds can be a plus to you.

Miscellaneous

 * Be wary of scammers and cheats. Do not join a guild that requires you to pay them. They are usually snobs or scammers. If you feel uncomfortable in a guild, leave! There are plenty of other guilds out there for you.
 * Guilds which are recruiting use several terms in their speech: TS (TeamSpeak, VoIP program), Vent (Ventrilo, VoIP program), Site (Which just means they have a website for their guild), GvG/HoH/TA (This means they are a guild that usually is busy doing Guild Battles, Hall of Heroes battles and Team Arena battles), PvE active (A guild that has a lot of PvE-ers), PvPvE (A guild that is doing active PvE as well as PvP).