I noticed that my students really struggle with "what's important" at any level of History. This document contains some tips to help them clear up that confusion when writing definitions or taking notes on individuals or events.
I explain to them, for instance, that events relate largely to cause and effect and explain that all events up to the beginning of an event relates to causes. The event itself is the fire, and the effects are the ashes left after the fire. This seems obvious to me, but I often find them talking about events DURING WWI as a cause of WWI because they don't understand that basic idea.
This will give them some general guidelines to help them write solid, thorough, relevant definitions for events and individuals in History.
Also available as a PDF document, if you want a quick clean copy. See the listing with the same title in PDF version.