Guilds; These are like a family they help you out with advice, levelling, most offer competitions for prizes but you basically join to one that will suit your style play, be it [trading], [PvP], [Levelling] or an all rounder.
Some will help with gear advice for different levels and how to make gold.
They all have a Boss Ring; a bunch of links at different level ranges to maximise your [experience] gain to level faster (maximum non-gold member: 8 EXP per boss hit, Maximum Gold Member: 10 EXP per boss hit).
You will be expected to post bosses up for people to hit and to hit theirs too, (thats team work). they Each have their own set of rules and do take a chance to find the active members and who your officers are and check your chat and private guild wall each time your on to find out the latest news.
You will find Joining a Guild easier to get your party member gear boost and fastest way to level as well.
Do take your time considering which Guild you choose however as joining and leaving different guilds regularily, makes it seem as if your just hopping to get free stuff as much as possible.
All guilds have at least 1 member who is friends with atleast 2 other members of different guilds and they do all talk to spot the cheaters out.