If the flood in the basement is relatively shallow, pump out the water using a submersible pump attached to a hose that leads outside the house. Turn off all electrical circuits for the basement before proceeding to prevent electrocution. If the service panel is in the basement, contact an electrician to remove the meter face and disconnect all power from the home. If you must disconnect the power, use a gasoline-powered pump.
Pumps and generators are available at tool rental stores. While some submersible pumps attach to a garden hose, using a larger diameter sump hose speeds the process of emptying the water. Gasoline powered pumps require a hose from the pump to the basement and a discharge hose to direct the water away from the basement walls.
If the basement floods due to localized flooding, wait until the floodwaters recede from the yard before beginning to pump the water. As long as there is standing water in the yard, any water you pump from the basement will leak back into it.
For minor basement flooding of less than 1 inch of water, use a wet-dry vacuum to pull the water into the vacuum's canister. Empty the water into a functioning basement drain, or carry the canister upstairs to empty it. Install a sump pump for a more permanent solution for minor basement flooding.