AVR-Chat

What is the considered wisdom regarding changing a port from output to 
input? I am trying to interface to a LCD display and attempting to 
read the busy flag which is available on the data lines of the device. 
I've looked around and some code just changes the DDR as required and 
some set the outputs of the port to all 0's before this so as not to 
get a flase reading. Is this a belts and braces approach or a 
requirement. BTW, I've tried both versions of changing the port over 
and the LCD does not function how I want, but it's a case of 
eliminating errors. Thanks in advance.