If you're stuck with the Apple logo (iPhone)

1. Do not perform a hard reset (holding home+power) when you're updating / downloading the system or any apps! You will end up being stuck on the Apple logo.

2. But somehow you're stuck with it, do not perform a restore like Apple tells you to, you will lose any data that's not backed up.

3. Put your phone to the side, unplug the charger, let it be with the Apple logo on the screen, and enjoy your day.

4. After it dies, plug the charger in, and it will be turned back on like nothing happened.