Ok first thing- the supplies you will need:
- Small Phillips screwdriver
- Case opener tool
- Pentalobe screwdriver (this is a 5 pointed star - newer iPhones have this instead of the standard Phillips)
I also recommend having a nice clean and clear work space, and to lay the screws and parts out as you pull them to keep them in order and to make sure you don't forget or lose anything when putting the phone back together.
Please remember before doing any work on the phone to power it off and pop the SIM tray out of the phone!
Now to start work on the phone itself. First thing you will need to do is take out the two small screws at the bottom of the phone. They are on both sides of the dock connector. (If you have a newer iPhone 4 this is where you will need to use the pentalobe screwdriver)
Once you have taken out the screws flip the phone onto its back side and push the back plate up and pull up to release the back plate from the phone.
Next, to pull the battery out, you will need to unscrew one screw that is holding the battery connector in place. Once done, pull the connector up to release it.
Now that the connector is out pull the clear tab on the phone. It takes a little bit of force but the battery should come right out. If you are still having problems, use a case opener tool and gently pry up to release the battery.
Next is to release the dock ribbon. There are 2 screws holding it in place. Unscrew them and lift the dock ribbon up.
We now need to remove the dock - unscrew the bottom screw on the logic board and pop off the lower antenna. I recommend just using you fingers and gently work to pop off the antenna.
You will now see one other screw on the other side of the dock unscrew and gently pull the dock.
Alright, now move to the top of the phone. You will see 5 screws that need to be taken out! That will allow you to pop off the ribbon container clip.
Once the clip is removed pull the camera.
You will now remove the one screw hidden under the water sensor (removing this will void the warranty) and another screw on the top right of the logic board. Once removed, lift all 5 cables from the top of the logic board.
Now gently lift from the bottom and pull the logic board out of the housing.
There are two more screws on the top right of the phone holding the vibrate motor in place - remove them and pull the motor.
We are getting close! Now to remove 10 final screws. 4 screws will be on each corner of the phone and 6 with washers down each side (these are holding the LCD frame to the bezel).
Once taken out use your case opener tool and glide it around the frame and the bezel. Once you get it popped up lift the screen out - BUT be careful of the ribbons on the LCD, there is a crack they must go to and you don't want to get them caught and damaged!
You have now completely disassembled your iPhone 4! Now you can fix, replace the screen, or even do a cool color swap.