I make sure that either WiFi or Ethernet cable are connected correctly. Afterwards I check if computer receives an IP address and make sure it is not 169.x.x.x. If there are no IP addresses, I check if network cards work correctly or if driver is fine. In case of WiFi not connecting or not being detected by the system, I first check if router is on and broadcasting then I perform a static drain of the laptop. In case of Ethernet cable not giving correct IP address, I test different cable and different socket in router/wall or different Ethernet socket in computer if present. If it is 169.x.x.x IP address, I make sure that DHCP is enabled and there are no custom DNS/DHCP settings present, unless required.