As above, write words, sketches anything to do with what you're creating, literally anything that comes into your head. I keep a sketch book on my all the time and doodle in it whenever I have the chance of get an idea. I wasn't meaning you shouldn't carry on, as any work is good practice.
Create some 'fake; projects, look up some creative practice briefs online (Berry posted a decent one on here for the fish Box). Just play around and have fun with it, rather than focusing on being too serious.
But learning some basic principles will really help.