To fix a cracked mobile phone screen, purchase the correct replacement screen and digitizer for the device. Remove the back cover, and tear down the device carefully, replace the cracked screen and reassemble the mobile phone.
A heat gun, scissors, small screwdrivers, double-sided adhesive tape and canned air are needed while fixing a cracked mobile phone screen. Remove the phone's back cover, and remove the battery, memory card and SIM card before removing the tiny screws that hold the motherboard in place. Gently pull the back frame away from the chassis, and remove any cables that connect the chassis to the glass. Keep visual cues to know which cable goes where when reattaching the unit.
Wave the heat gun over the adhesive joint of the phone's front frame, and pull it apart to remove the broken glass. Attach fresh two-sided adhesive tape strips to the bezel, replace any seals and foaming pads, and attach the new digitizer and glass to the bezel by pressing it firmly. Reattach all parts, and reassemble the chassis and frame.
While reattaching cables, look for solid connections and clasps. Flip the clasp up to open it, reattach the cable, and flip the clasp down to hold the cable in place. Replace all screws, insert the battery, memory card and SIM card, and snap the phone's back cover in place.