Ignore the little jawa... he gets his rocks off insulting people and telling them how much they suck. *whispers in ear* (He has a yoda weewee...)
One big question you should ask yourself is "what type
of clan am I looking for?" These are the main three I'm familiar with:
clans (and yes, we know... they all suck in JA) who play against each other in tournaments & ladders. Often they might specialize in a specific game style, though many play all or several styles. They have scheduled practices, focus highly on teamwork and strategy, and take their successes or failures very seriously. Here you will usually find the best and most skilled players, but alas... also the most arrogant and confrontational.
2) Just for Fun
clans that are basically a bunch of people who like playing together with custom maps/skins, and usually the game style doesn't matter. They might have a website and/or a private/public server with an open schedule; or they might have scheduled matches and trainings. Sometimes they'll challenge another clan to an event and have a "competitive" experience... in any case, here you will usually find a somewhat relaxed and freespirited type of player, but also a lot less focus on the skill of playing - that's not to say they aren't good players though, or might participate in tournaments/ladders. Sometimes a newer clan that perceives itself as "competitive" will more likely fall into this category without realizing it.
3) Role Playing
clans (RP) that create an entire world or story within an era of the Star Wars universe, where each member takes on a role to play within the group. Usually these groups schedule events in a private server that are fairly high on dialogue and intrigue, while low on action and mayhem. These events can be quite enjoyable when done well, and a stimulating change from the regular "all action" gameplay - and they can also digress into quite boring and chatty IRC session when done poorly. They tend to use lOts of custom maps, skins, and mods to create their worlds within an FFA game style environment. Often there's a farily strong hierarchy to the group, as well as a host of rules to follow, which many in these groups feel are necessary to keep things focused and on track. Here you will be treated with respect and honor, which is both a blessing and a curse... it can get a little pretentious and stuffy at times.
Now there are some that fall outside of these three of course, but this covers most of the ones you'll come across. Clans tend to lean either toward the Light or Dark side... I've rarely come across those that blend the two together, though some of them do try. Considering all of this info could possibly help narrow down the search for you, as well as save a lot of wasted time heading down the wrong direction.
Clans have the potential to be a lot of fun; but they also have the potential to be a royal pita. A lot of the servers out there are supported by clans. Generally, if you find a server that you enjoy playing on regularly, and the people are welcoming and nice to you, then walk up and ask a member how one joins their group. Usually they'll give you a website address where you can read their information. Sometimes the welcome screen on a server will have a web address listed - write it down if it's one you like. A good clan will usually have it's own forum, or at least a requirements page with some email contacts. The IRC channels are good to find the more competitive clans, while many will often use MSN, AIM, or ICQ to connect privately. I would recommend getting a copy of Trillian Basic
if you're serious about finding a clan - it's an IM client that covers AIM, MSN, Yahoo, ICQ, and IRC all in the same interface with no ads.
If you clarify what you're looking for here in a clan experience, maybe someone can point you in a good direction...
May the Force be with you.