If you are using Wifi, switch your router off and switch it on again.
If you are using mobile data, turn Airplane mode on and off to reconnect.
If you are using Wifi, move closer to the router or move it closer to you. Keep line of sight with your router.
If you are using mobile network, move to a place with better signal and avoid being underground.
Check the Wifi networks available and connect to the one with the strongest signal.
If you are currently using a Wifi network with a weak connection, such as a public network, switch to mobile network.