Your best bet is the manual for your router. The higher end Drayteks are very good for this (28xx can and have very good manuals), pfsense looks good too. Mikrotiks work but I find out is very easy to make a mistake. I have found a few that have been left rather exposed...by pros too.
To test if you have been successful I recommend plugging into your untrusted network with a laptop and scanning with nmap (or zenmap for a gui. You shouldn't be able to see other devices).
Enterprise type WiFi devices like Unifi allow you to set up separate wireless vlans too. In fact Unifi WiFi to Unifi security router is probably the easiest way to get this set up.