I just got myself a flash gun for my dSLR. I realise that I don't quite know what to do with it. What should I do to get used to it, and to learn about how to get the most out of it?
Read the Strobist 101 series on the David Hobby's Strobist site. http://strobist.blogspot.com/2006/03/lighting-101.html
He provides an amazing amount of knowledge on use of small flash. It also provides some homework assignments that can serve as inspiration to help you get out and use it.