While you remain an LW (short for LittleWho: meaning a junior player, yet to have completed an apprenticeship) and prior to choosing your long-term guild membership, it is advised you take advantage of the "selections" opportunity.
Syntax: SELECTIONS to see all professions available for skill sampling.
Once you start a full apprenticeship and join a guild, you will be bound to that guild's professional skills - and it will define much of your future Avalon life. It is wise, therefoe, to use "selections" to sample as many professions as you deem sympathetic to your character's role, alignment and outlook. Type SELECTIONS and you will see a list of professions available to you, to be selected for a short sample in which you will gain - temporarily - a respectable group of skills (guild/profession appropriate); so you can look them over in detail and test out between thirty and a hundred profession-exclusive abilities.
Syntax: SELECT followed by the profession.
You type SELECT and then the name of the profession (as per those listed when you type SELECTIONS; keeping in mind you can only sample a profession once). This will begin a short-term "junior apprenticeship" in which you will immediately acquire the standard range of profession skills - at a high enough level to enable you to get a feel for what you should expect if they were the foundation of your permanent guild career. You are allowed to spend two Avalon days (or two hours, game time) using your junior "selection" skills-set.
Syntax: SELECT NONE.
Declares an end to your "selection" of a specific profession, handing back the skill-set provided as a sample in readiness to either SELECT the next profession you wish to explore or because you have learned enough to take the big step of starting your fully-fledged apprenticeship.
See also HELP APPRENTICE and HELP ENROLLMENT for more info on the crucial "which guild" decision and how to enroll once the decision is made. The HELP GUILDS list will give you an up-to-the-minute list of all public Avalon guilds, their leaders and divine patron and HELP 11 and HELP 14 will display the helpfile contents for the two sections on Guilds and the Professions respectively.