- Open "System Preferences."
- Click on "Network."
- Click on the Gear icon in the lower left and select "Set Service Order."
- Set Wi-Fi to first position and Ethernet to second.
NOTE ABOUT NETWORK SETUP: Separate the two networks by setting the wireless router to use a different subnet mask (e.g. 255.255.0.0) while also setting the DHCP range of addresses to assign from a different pool (e.g. 192.168.0.100).
NOTE ABOUT SHAREMOUSE: Make sure to set Sharemouse to use the LAN addresses as using WiFi will result in serious lag making it impossible to use. To do this, open Sharemouse settings, click on "Clients" and make sure only the IP addresses from the LAN are in the client list. Also, make sure to setup static IP addresses for your Ethernet connection so you define clients explicitly in settings.