Today, the most common method for hydrogen production is steam reforming of methane. It requires liquids or gases containing hydrogen, for example, natural gas. Under high temperature and pressure, the fuel reacts with steam leaving you with hydrogen. Such hydrogen is called «blue».
Gasification is the oldest method of producing hydrogen. Water vapor passes over hot coal at a temperature of about 1000°C. This causes a reaction that separates hydrogen. The process is not the most environmentally friendly, so the hydrogen extracted in such a way is often called «gray».
There are other methods of producing hydrogen, for example, «yellow» hydrogen is produced using atomic energy.