I'm adding to tips for using phone cards

Keep in mind that you can even make local phone calls with your phone card too, just remember to include the area code when dialing the number you want to talk to. This is especially useful if you come to a pay phone, but have no change.

Using phone cards on cell phones to make long distance or international calls:
Keep in mind every minute you have a connection will be deducted from your phone card AND you will be charged per minute by your cell phone carrier.