You could start by writing a routine that scans your port for a keypress, and then jumping to a routine that blinks a led.

If it does not work, single-step through the program (eventually using a simulator) to see where it goes wrong...

If it works, try the next step (ie put something on the lcd if key is pressed..)

Continue step by step until it works, and then try the next step....

hope this helps...

BTW: making a flow-chart could be handy too...

regards
Patrick