best place to start is the data sheet of the lcd itself. read and understand what you can, then start experimenting with it and discover what you didnt understand.
Since the display is output device looks silly to me to read the busy flag although i done it both ways.
Lots of info and examples are available on the web also about LCDs for both assembly and C.
Check this site out:
http://home.iae.nl/users/pouweha/lcd/lcd.shtml
Good luck
Mahmood