Change your MAC address in public
Your MAC address uniquely identifies your computer on a network. On WiFi, this address flies through the air for everyone to see. The wireless router uses this address to map an IP address to your machine. It's a good idea to spoof your MAC address when in public.
At the coffee shop, when the barista asks for your name, you don't give them your social security number. You give them your first name, initials, or even a nickname. Practice similar obfuscation when connecting to the internet.
By default, your laptop ups your network interface when booting. Figure out how to prevent this. When your interface activates, it tries to find the gateway to request an IP address. By this point, it's too late, and your real MAC address is cached by the WiFi router, and stored by anyone malicious. Therefore, manually bring up your interface after you have changed your MAC address.
On Linux, it's simple to change your MAC address with macchanger.