Frequently Asked Question
Lock your computer if you get up Sick of your "friends" going onto your computer at work or home and posting things on your Facebook/Twitter page on your behalf? It's certainly an annoyance, but an easy one to prevent.
Windows + L will lock your system right away, requiring a password (if you've set one) to log in again.
On macOS use Cmd + Option + Power to log off. On the latest revision of macOS (High Sierra) a quicker option to simply lock the screen was added which works using the shortcut Cmd + Ctrl + Q.
See who is logged on to your router Software such as Wireless Network Watcher makes this particularly easy and even has alarms for when someone new appears. You can also do this by logging into your router (common router IP addresses) and checking for a list of wireless clients which should display the name of the device, its currently assigned IP address and its MAC address.