The ones I usually always see is what is the fastest and most efficient way to farm pretty much anything.
Fastest way to get through the MSQ and catch up.
Fastest way to get endgame gear late to the party.
How to get into endgame raiding with no experience at all and how to find the resources necessary.
Not knowing when primetime is for certain activities and end up waiting in queues for much longer than they need to.
Not knowing the benefits of DC Visit and World Travel, and when you might want to use them.
EVERYTHING related to PvP.
ANYTHING related to endgame. The game doesn't teach people how to play their jobs very well.
The classic is what jobs are best and why. Which jobs are most new player-friendly? Which jobs can I not get yelled at for not being good at, ect.
All the different quest markers on the minimap, how to find the Aether Currents, and how to tell if something has an unlockable or meaningful reward. (The number of people that don't have flight when I do map parties is kind of staggering)
I see a lot of sprouts asking how to get involved with RP and how to find mods but that one is uhem. Goodluck.