A lot of the stuff an admin deals with day to day isn’t based on what we know, but on what we can find out. We spend our days researching problems and looking for solutions. What are the best resources?
Each operating system vendor has their own knowledge base or forums. For example, HP has the HP ITRC (IT Resource Center) which provides a one stop source for forums, documentation, technical notes, patches, and more. Other vendors have similar portals for technical support.
There are a number of books that one can turn to as well; however, books on certification may often be overlooked. These books cover more obscure areas of an operating system and its maintenance, and can point you in the right direction when nothing else will. Many times, these tomes are also written to be on-desk references as well, and as such include the author’s experiences and knowledge beyond what is needed for certification.