Anyone who does not have a class yet may go to Certimene, the Guild administrator, in Delos, and ASK CERTIMENE JOIN <guild>. You will be inducted into the guild, (unless you're a Nightstalker, then you may only join the Bloodborn Guild if you wish to) and will gain two of the three guild skills of that class. Until you have gained the 21st circle of experience and learned as much as you can in both of the guild skills you have gained, your ability to learn those skills further will be limited to the level of Adept, and you will not be able to use any guild-related commands except for guild novice tell (GNT <message>).
As a Novice, you may quit or be kicked out of a guild, and you will be refunded 90% of the lessons that you spent learning the guild skills that you lost. Further, Certimene will only grant you entrance to a particular guild once. If you've left or been kicked out of a guild, you will have to ask a guild member of the guild to induct you.
You can graduate out of novicehood in your guild once you have achieved Level 21 and are 100% Adept in both of your guild skills. Type GRADUATE FROM NOVICEHOOD to do so whenever you are ready.
For reference purposes, the two skills that novices gain are, by class:
Atabahi - Lycanthropy and Ferality
Bahkatu - Lycanthropy and Ferality
Bloodborn - Mentis and Corpus
Cabalists - Numerology and Necromancy
Druids - Metamorphosis and Groves
Indorani - Necromancy and Tarot
Infernals - Chivalry and Necromancy
Luminaries - Spirituality and Devotion
Ascendrils - Crystalism and Elemancy
Sciomancers - Crystalism and Sciomancy
Monk - Kaido and Tekura
Priests - Spirituality and Healing
Paladins - Chivalry and Devotion
Sentinels - Metamorphosis and Woodlore
Syssin - Venom and Subterfuge
Teradrim - Earth and Sand
Vampires - Corpus and Mentis
Zealots - Tekura and Telepathy
See also: Guilds, Certimene and Nightstalkers.