If you want to start immediatly (the "trial and error" method, like most of us do
), the best thing todo is to look at already made scripts (start with the small ones) and try to understand them. Change some things in them, etc. All this with the documentation besides you to look up each and every function, property and method you'll come across.
Besides the Plus! scripting documentation, you also best download the JScript documentation:
http://www.msgpluslive.net/scripts/view/152-Windo...ipt-Documentation/
Since you say you already made some small scripts, it probably is also a question of imagination. Think of simple things you want to try, or improve in your existing scripts. eg: Add an extra option for something. Try to make a sorting routine for that list you've used (just an example). Add some commands to your scripts and add a nice handling routine for when the user types wrong parameters, etc...
Happy scripting