The G-Shock series of watches is produced by Casio. Most current G-Shock watches are powered using a built-in solar panel and do not require battery changes, but models manufactured prior to 1997 require the occasional battery change. The process is delicate, but with the proper concentration, it can be done fairly quickly.
Use a small Phillips screwdriver to remove the screws from the backplate of the watch.
Remove the backplate.
Use the tweezers to unclip the battery holder and remove the dead battery.
Insert the new battery in the back of the watch.
Use the tweezers to press the battery holder back into place to secure the battery.
Look for the letters "AC" somewhere near the battery. The AC labels what is known as the AC contact. AC stands for All Clear. Place one point of the tweezers on the AC contact and the other end on the exposed part of the battery and hold the tweezers there for 3 to 5 seconds. This resets the internal memory of the watch hardware.
Carefully lift the watch until you can see the face of the watch. Don't turn it over or you may lose some of the very tiny parts inside. If the display is blinking 12:00, you have reset the watch properly and can move on to the next step. Otherwise, repeat step 6.
Carefully remove the gasket and check to see that it isn't damaged in any way. If the gasket is in good condition, lightly grease it and return it to the watch.
Place the backplate back on the watch.
Return the screws to their original positions and tighten them with the screwdriver. Set your watch to the proper time.