first of all, read everything you can get your little hands on. then, install it, download a few themes, get your hands dirty customizing them to how you want them to be, then when you think you're ready, read more. and THEN, start designing your own theme. and during that process(yep, you guessed it!), read more. that's it. it's a lot of reading, and trial and error. and don't worry, with litestep, you can't really "break" anything. if a theme stops working correctly, and you can't figure out how to fix it, if nothing else, delete the theme, and grab it again from here or another site. but that's a last resort. everything should be fixable, if you use all the resources at your disposal.