Make sure you know which model you are working on. An iPhone 6 is not the same as a 6s—the instructions are different and the parts are not compatible. If in doubt, find the model number of your iPhone.
Discharge the battery below 25% if possible. Below 25% charge, there is far less risk of a dangerous fire in the event you accidentally rupture the battery cell.
Be mindful of electrostatic discharge (ESD), a.k.a. static electricity, which can silently destroy delicate electronic components. Use ESD-safe iFixit tools as instructed to greatly reduce the risk of accidentally damaging your phone. If in doubt, wear an anti-static wrist strap and work on an anti-static project mat. Don’t perform your repair on carpet (or wearing a shirt that you just pulled out of the clothes dryer). Remove rings and other metal jewelry from your hands. If you live in an area with a very dry climate, it's even more important to take all of these precautions.
Have a strategy for keeping track of screws and parts as they come out, so that they go back exactly where they came from (the Magnetic Project Mat is our favorite solution).
Always disconnect the battery as soon as possible. This step is part of every iPhone guide—don't skip it!
Be mindful of where you put your pry tools. It’s easy to damage and/or dislodge logic board components with wayward prying. If you need to pry something up, put your pry tool directly underneath it, and use the case/housing for extra leverage if needed. Never use other logic board components for leverage.
Be extra careful with the Home button/sensor and attached cabling. Most other components can be replaced or repaired if you accidentally damage something, but the Home button’s TouchID sensor is securely synced to your phone’s logic board at the factory, and can only be replaced by Apple or an Apple Authorized Service Provider using specialized equipment. (On models prior to iPhone 7, you can replace the Home button yourself, but you will lose Touch ID function.)
Handle parts only by the edges, or use gloves or tweezers. Your natural fingerprints and skin oils can interfere with certain device functions, spoiling your repair. If you touch something by mistake, don’t panic—just clean it with a little isopropyl alcohol using a lint-free cloth or coffee filter, and allow it to air dry.
Carefully inspect your replacement part and make sure it exactly matches the part you've removed.
Peel off any temporary films, liners, and/or tapes.
Certain smaller parts such as brackets, spacers, and gaskets may need to be transferred onto your new part before reassembly.
Be very careful to pry only under the flat edge of the connector, and not under the socket itself. If you pry under the socket, you will separate it from the logic board, causing permanent damage.
To reconnect, align the connector carefully over its socket and press down with your fingertip—first at one side, then the other—until it clicks into place.
Do not press down on the middle until the connector is fully seated—if it's misaligned, the connector can bend, causing permanent damage.
Don't overtighten the screws. Very small screws—such as those used in phones and tablets—require very little tightening force. As soon as you feel resistance, give it another quarter turn or less and then stop. Overtightening will strip the screw threads and may damage your iPhone.
When reassembling components, don’t try to force it. Using too much force is a fast way to break your device. If something’s not quite going together right, back off and investigate. Make sure you have the correct part for your particular model. Look for obstructions and try to determine where the problem is. Back up a few steps and try again.