SP chains + either releasing a players guide to how the party search function works (since no one uses it) or go back to FFXI's method of seeking for party/members would help a lot to promote party play outside of guild leves.

One problem I find with FFXIV's current system is it really doesn't promote much socialization at all outside of your own linkshell/group of friends. Most likely if you do leves on a regular basis you are doing them with a set static group or soloing. Even doing Behest with random players you just say 'hello' in the beginning, some small chit chat sometimes in the 5 mins before start... then it's all business because you have to spam 1 1 1 1 1.

In FFXI when you were leveling to 75 you were interacting with new and different people almost every single day. And with auto-attack people actually had time to type in party.