I encourage you to browse the stickied thread listing LSs on Ragnarok.
Three that I've had good experiences with, just speaking for myself, are:
1. Axiom (http://www.axiom-online.org/forums)
- I'm biased because this is my primary LS. We are a medium-sized group with a broad mix of vets and newer players, with plenty more in between.
2. Musketeers (http://ffxi-musketeers.com/forum/index.php).
A medium to larger shell that is nicely organized. Although they have mostly veteran players, they have their share of newer ones to benfit from the vets' wisdom, too. One thing to be aware of: last I heard, applicants needed to have an existing member of Musketeers as a sponsor. But do check them out; don't be put off by that.
3. Triumvirate (http://www.triumvirate-forum.com/phpBB2/).
A somewhat larger shell with a wide variety of experience-levels.
Check them all out; shop around! Your linkshell is your in-game family, so it's important to find the best fit.
In-game, I am Grommet (when I'm not on a mule!). Best wishes. Edited, Oct 15th 2008 7:10pm by MJS