The very first thing you should do in the event of water damage is locate the source of the water and ensure that the flow of water has been stopped. Cleanup can't happen if water is still actively pouring into the home. After the water has been stopped, it's good to cut the power to the home if there is any standing water. Electricity and water can make a dangerous combination. If either of these tasks puts you at risk, wait for a professional. Finally, take as many pictures as possible before starting any potential DIY cleanup as long as it's safe. You'll want to start cleaning right away if possible, but you'll also want your insurance company to be able to see the initial extent of the damage before any cleaning occurs. Once pictures have been taken and the area has been deemed safe, remove as much standing water as possible and set fans to begin the drying process.
If you're thinking about trying to do the cleanup on your own, you'll want to consider the volume and the water source. A tiny patch of clean water can usually be handled in-house, but a basement flooded with sewage needs to be handled by a professional. It's important to remember that even small amounts of water can hide in cracks and crevices and within porous materials, creating the perfect breeding ground for mold and mildew if not dried completely. As far as the water source, if the water is grey or black, it should never be handled on your own. These waters contain contaminants that need to be properly cleaned to ensure the safety of the home and everyone in it.
If you've determined that the issue is beyond the scope of your abilities to handle, it's time to contact your insurance company. You'll want to find out what kind of coverage you have for the loss and what your deductible is. If you decide to file a claim, you'll be assigned an adjuster to handle it. Your insurance company often puts you in touch with a preferred restoration vendor, but sometimes they'll advise you to find one on your own.
A restoration professional will be able to work directly with your insurance company and you to ensure the job is done properly. A project manager or technician will assess the damage and help determine the most appropriate course of action. Standing water will be extracted, and drying equipment will be set right away, so the damage doesn't become worse. Once everything is dry, unsalvageable materials will be removed, and everything else will be cleaned and sanitized to prepare for reconstruction.