So far I have not taken any lessons (either during College or Uni) for Interaction Design or HCI, but having developed software for a few years now I have picked up on some of the techniques. I've also read a bit about it and spoke to other developers. One guy I spoke to had done a course in Interaction Design that he said was very useful (though maybe a bit boring work to get through). I'm just about to try designing the UI for the small program I am planning to write, I'm going to take his suggestion and try drawing it out by hand first.
I wonder if drawing it by hand rather than on a pc really makes much difference, personally I don't think it does. As long as you are not using the IDE that you could be tempted to add code. So maybe using a plain drawing application, or maybe just the shapes you can use in a word processor. But until I have tried it a few times I cannot say for certain what I feel are the advantages or disadvantages.
My next post will include a copy of my hand drawn design. As a pre warning, it's not likely to be great since I can't draw very well, could be that I am left handed or just that I never put in enough effort. Or as some people think it's a talent that you're born with, though that's a whole different topic :).