1. Common issues that can cause network connection problems include unplugged network cables, websites being temporarily offline, and IP address conflicts between devices on the network.
2. To diagnose network connection issues, one should check that cables are securely plugged in, network cards have lights indicating connection, and multiple websites load properly rather than assuming a single site issue.
3. Troubleshooting steps involve using tools like cable testers and multi-testers to check network components, releasing and renewing IP addresses if there is a conflict, and contacting internet providers regarding potential outages.