Take the other person's namecard with both of your hands!
This is something I leaned during my first company's freshman orientation. :-)To show respect, take the other person's namecard with both of your hands (not one hand). You would introduce yourself first and give your namecard (also by using both of your hands) so that you have both of your hands free to take the other person's namecard. The process of exchanging namecards is an important opportunity to express respect! (I actually felf very different when I saw people exchanging namecards casually with one hand when I started doing international sales outside Japan.)