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.
I VALUe the bitcoin a lot , like one of source of income for my family , its like other type of money but this one serves us a lot and help us a lot . like myself I value it and care of it everyday because I know it will be hard for me without the bitcoin as source of my income.