Before you go start taking apart your Wii, make sure you got all the small problems fixed.
- Make sure your Wii disc is clean. This means no fingerprints, smudges or scratches. If it is dirty, you can clean it with a soft cloth. Start from the centre and wipe it outward. Wiping in a circular motion will create scratches.
- Give your Wii a reboot and then try putting the disc inside.
- Keep your Wii up to date. Check for system updates and always install them on your Wii.
If you are still getting a disc error then here are some solutions.
After long play sessions, the Wii can over heat causing connectors to malfunction. Make sure you Wii's exhaust fan is properly ventilating and nothing is obstructing it.
Cleaning the lens
The best way to clean the lens is to buy a official cleaning disc. If you are feeling adventurous and want to try cleaning the lens on your own, you can try this...
A jet of air from a compressed air can may also clean the lens, but I would advise against this because shooting air inside the Wii can force the dust to spread to other parts of the console.