And not just delete the images from the card. You must format it in the camera.
Yes, only recycle cards by reformatting in camera. You can also delete individual files while shooting, but don't do any of the following...
1) Delete All in camera
2) Delete individual files in computer
3) Reformat in computer
Instead, do only the following
5) Delete individual files in camera
6) Reformat in camera***
*** By far the most reliable thing to do.