For the back, I leave the clear plastic sheet that ships with the phone (actually I doubled up and apply the front plastic sheet on top of the back one) and cut the tab so it wont stick out.
You can use a three hole punch to punch out two holes for the camera and the flash.
Step 2: Electrical tape
Cut a 4.5 cm x 0.3 cm hole somewhere. This will be the opening for the bottom speaker, mic, and ipod connector. The location depends on where you want to seam ends up. I decided to have the seam on the simslot side so I cut this slot about 6 cm from one end of the tape.
Step 3: Simply align the slot with the bottom speaker, mic, and ipod connection
Step 4: What about the other "holes" needed to cut
Briefly cover the mute button, use the utility knife to lightly nick the margins of the mute button. Then put that portion of the tape on your cutting mat (or desk) and cut a small rectangular hole. Resume wrapping.
Repeat for the other holes. I dont use the headphone jack so I just cover it. But you do need to open a small hole for the top noise-canceling mic though.
When you come to the on/off button, again reduce tension.
Leave 1 cm overlap with the tape ends.