Document and label cable and screw locations
There are a lot of cables in mobile devices. There are cables for antennas, drives, video, etc. so document where each cable is connected to.
Different sizes of screws are used in different locations so keep track of the screw locations. There may be screws in unexpected locations so documentation is key.
Laptops generally disassemble in sections. For example, you take off the outer shell, then the keyboard, then the video connectors, and so on. It’s helpful to take pictures or record a video while working on the devices so you know how to reassemble everything. It may be helpful to organize parts in a container with separate sections. As you disassemble a component keep the related screws and items in a one section. Then as you disassemble another component, keep the related items in another section. It’s recommended to use a sectioned container that is capable of being sealed to prevent accidental misplacement of components.
Refer to manufacturer resources
The manufacturers may provide step by step repair guides. Otherwise, other helpful folks may have posted written guides or videos on the internet.
Use appropriate hand tools
Specialized tools may be required for these small components in mobile devices. For example, you may need specialized small screwdrivers. You may also want to use a magnification tool to allow you to see the small components easier. A tweezer is also recommended to assist in handling the components. An anti-static cloth is also recommended to protect delicate components.