Hydrogen is a great way to store energy but it is not easy to make.  The most widely used process is steam reform.  Super hot steam reacts with natural gas to make hydrogen and carbon dioxide.  It is currently the most economical and efficient process.

Electrolosys is another well developed option.  It uses electricity to split our favorite molecule H20 into pure hydrogen and oxygen.  It is a very clean, pure process.  However, electrolysis actually consumes more energy than it produces.  While that sounds bad, it is a mistake to discount electrolysis on that fact alone.  Steam reform is limited.  Its operation and economics depend on the supply and price of natural gas.  Electrolysis can use electricity from any source whether traditional power plants, nuclear, or all types of clean renewable energy.  This flexibility allows electrolysis to take advantage of cheap, off-peak electricity to produce hydrogen much cheaper than steam reform.  Electrolysis can also be paired with renewable energies to produce hydrogen without the creating carbon dioxide.

Several very interesting alternatives are also under research.  Bio-hydrogen utilizes microbes to split water into hydrogen and oxygen.  Photoelectrochemical water splitting uses sunlight to directly split water.  Solar thermal water splitting uses highly concentrated sunlight to split natural gas into hydrogen and carbon dioxide.

True to the alternative energy industry, we probably won't see one clear winner.  Technical developments in the coming years will create advantages but it is likely that several methods will be vaible depending on the situation.  It is most important to know your options and how they fit with your goals.