Owners of an Apple MacBook might be interested in this: By default, a MacBook wakes up from sleep mode when you open the lid. This is dangerous because if the machine is inside a suitcase, it may produce a lot of heat if it wakes up by accident.

You can switch off this behavior by typing in this command into the Terminal application:

sudo pmset lidwake 0

The machine will ask for the administrator password (for sudo). After the change, when you open the lid, you will notice that you need at least one keystroke or mouse click to start the machine. You can undo that change by

sudo pmset lidwake 1