How do I delete single specific photos from my iPhone 4?
To delete a specific photo on your iPhone 4, open the Photos app in your phone and select the Camera Roll. Tap the button located on upper-right corner of the screen and select the photo you want to delete. You can get more tips at http://howto.cnet.com/8301-11310_39-20013723-285/iphone-tip-select-multiple-photos-to-share-or-to-delete/.
Click each picture that you want to delete one by one, tap the screen of the picture to view the options, and click the trash bin.