It seems to me there are certain basic things that all Linux users need to learn, but I don't know of any central location where they are taught.
The first of these is to read logs. I've seen countless questions about problems, particularly server problems, where the poster has obviously never thought to consult the relevant logs. Yes, Linux has many logs and learning about them takes time and effort. But I don't have a lot of sympathy for would-be server administrators who don't look in /var/log for hints about a problem before posting here.
A useful technique that seems untaught is submitting error texts to search engines. When I see a program throw an error, I find searching for the error text often leads to the correct solution. Again this should be a prime tool in any administrator's arsenal.
Another pet peeve concerns the fact that few users seem to consult the reams of existing Ubuntu documentation. Many questions have extensive pre-existing solutions described in the Ubuntu help documents, yet the questions get asked here again and again. I've wondered whether some "sticky" FAQ threads might help, but my general perception is that there are a lot of people who just post questions and never think to consult documentation. Oftentimes seemingly simple questions like how share an Internet connection with Ubuntu requires a fairly lengthy set of commands and edits to configuration files. Rather than repeat that array of material here, I usually just point the person to the relevant help document. If that's bad form, so be it.
I've already expressed my opinion about rude posters who ask a question then vanish forever. In any given week I'll see half-a-dozen or more threads opened and then abandoned. Oftentimes the only response is mine. Dealing with such rudeness is tiresome to say the least.