As a leader of Marvels on Leviathan (Remora before that) for the past couple years, i find these suggestions to be most helpful.

Ask the person what they need and if you can help them at that moment then do so. If its something that requires more than an hour of more than 1 or more person's time then schedule a run on your forum (if you have one)

If this person needs something like a nysle isle floor climb or any mission that requires time to complete. Then start a static and keep to it till finished.

If people ask for help and you don't see them helping others then politely in /tell explain to them that in order to get what they need, they first need to help others get what they need done.

If your in any leader capacity, the best way to get your people helping each other is to lead by example and help those before yourself.

Any group that is going to last 6 months needs a strong foundation.
Lead by example.
Invite friendly and helpful people
Help out those that are below lvl 60 so you can have them help out in return when they become lvl 80+
Never be selfish and egos are not needed.

Hope this helps out anyone, whether your a LS leader, sack or pearl.