Switch off your phone.

If your screen is cracked you want to cover the front panel with tape to protect yourself from glass shards and get a better grip to lift it.

Use an iOpener to soften the glue on the edge of the display. Concentrate on the sides first and then on the bottom part.

With an iSclack or a suction handle you can lift the display a little bit to get in the gap with an opening pick.

The phone screen is composed of two layers (glass and display). Ensure that you are removing both layers and not splitting the two layers.

In the beginning just insert the tip of the opening pick and slide along the side to loosen the glue. Leave the top and bottom alone for now.