I did this by just playing through franchise/season mode. No matter what you're going to get everyone's card sooner or later. Otherwise here are some tips.
1) You can check out the requirements for each card by flipping to the back. There are two ways to get every card, so you can check those out. You can unlock cards in any mode but exhibition mode.
3) You can get a buddy to help you out online. Just let him be aware of the requirements for you to unlock the card and then go ahead and work towards them.
You can view a great achievement guide and CARD GUIDE here -
http://pwnpros.com/index.php?option=com_content&view=art...