Apart from the general information about posting on forums, which people don't usually read, I wonder could GNHQ send a message to new members suggesting if they start a new thread that they come back at least once to respond. It could be added to "Netiquette" section, though I suspect it wouldn't be read - an e-mail might work better.
I think sometimes people join specifically to ask about a particular problem and get lots of replies - often getting up to 100s - without ever responding. They may or may not actually read the advice, but it's frustrating for members who have spent time composing a considered reply, not knowing if OP has read it.
Lack of public toilets in towns.
Passports not in the drawer I always keep them in. Turning the place upside down.