I think that the most common way to value Bitcoin is like valuing other currency by another currency.
Seeing to it that we all know all the factors that causes or affects supply and demand equilibrium.
Also the time we hold bitcoins. Time is very important factor.
bitcoin is almost the same as the usd currency to local currency which always changes its price. but bitcoin value is much more valuable when compared to usd because bitcoin is very rapidly changing its value. many people take advantage of price fluctuations in bitcoin to serve as a very promising investment.