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 bitcoin because it my source of suplementary income. It gives makes my family financially stable. I have a regular jobs but this cannot support our needs sometime we make loans just to make ends meet. My bitcoin earnings provides me motivation to work harder.