Shut off the hot and cold water valves underneath the sink by twisting them clockwise until they are tight.

The appearance of these valves will differ from sink to sink, but most operate the same.

To test that the water has been completely shut off, try turning on the faucet like you would normally. If no water comes out, you're in luck!

When reopening the valves after the repair, leave the faucet in its on position. This will prevent pressurized air from building up in the faucet cartridge.