Have fun!

Leaders need to remember to take time for themselves too.

Be willing to listen with patience. Sometimes it is like being a parent... or a cat herder. :3

Be willing to help those who need it. Don't just wait for them to ask for help; be proactive and know where in the game your members are and what their interests are.

Don't be afraid to delegate!

Try to have a 'focus' of sorts for your FC. Whether it's rp, endgame firsts, all lalas (lalas are friends, not food ), etc.

Be transparent in leadership. Be up front and honest and respectful of your FC mates. Have solid reasons why you make the decisions you do.

Be a cheerleader. Everyone's energies in the game flag at some point. Show them you care! Don't berate anyone. Watch for bad feels or low morale and see what you can do to mitigate it.

Say Hi to everyone. Spend a little time running dungeons or doing events with everyone if you can. (My FC has about 80 members currently as a point of reference.)

Rank and hierarchy - your mileage may vary. I use lots of "vanity titles" in my FC to recognize those who really help out and are generally awesome people or have achieved some rank in game (example: Gold Chocobo, Monky King, Yojimbo, Sensei, etc.)

Use outside static communication like FC website or the FC forums on Lodestone. This is a good way to coordinate stuff if you have many people who play during drastically different times. Also, group photos are fun!