Share your experience!
Three broken nails later and it's not getting any easier. Any help would be most appreciated.
Try to get the bottom of the back cover loose according to the instruction on page 8 in the user guide:
http://www-support-downloads.sonymobile.com/st23/userguide_EN_ST23i_1265-3544.2_Android4.0.pdf
Then it's just to lift the cover of the phone.