Any possible way to stack Motor Driver shield L293D with Xbee Shield v03 on arduino?
Read the documentation for both boards. They should list the pins used. Their associated libraries will define variables to which you can assign non-conflicting pins. Review the sample code provided as well. Usually, the sample code included setting the pins to use, even if the code only sets them to their default. 

There is another possibility. I don’t think this is the case, but I’ve run into this issue with different shields. If the shields use I2C, they may need to have jumpers shorted to set an address.