I think the key is, that they need to be doing something regularly enough for them to feel the need to learn it and not keep asking. We do reporting so little that they always forget things, checking result date, hitting calculate, how to access them! simple, obvious things. whereas registers is quite well embedded in their brains now as they need to do it every 40 mins.
supplying comprehensive guides just doesn't help as it is too much hassle when it's quicker to call someone else for help, or ignore the problem until it's urgent, then call someone else. that's why i've tried to push the snippets of info route. we used to have a massive manual for general IT usage at the start of term for new staff, covering info from which mapped drives are for what, to adding printers, sharing docs, using email etc. the guide is lost or never used. We're trying to put in online now, so that you can just go to a knowledgebase area and jump to the mini guide on adding a printer. This has the benefit that it's quick and those that are too embarrassed to ask for help, don't flounder on simple hurdles.