i believe that most people have different approaches but work along the same keyfactors. For me the these factors are:
for domains without content or development:
extension
name/length
sound/ ease of branding
possible positioning in the market/ product driven?
OVT & Alexa & Google Results
Parking Revenue
of course there is more, but thats top secret *shhh*
for domains with content:
all the above plus,
traffic
revenue
adsense
SEO optimization
content itself
affiliate or self driven page
...and so forth.
you will get to develope your own "formula" over time, most of us are head-on with evals, so stick with NP, i've learned a ton from here, and brought my education+experience back to the board, which is basically what everyone else does here, making NP a tremendously strong board. :imho: better than any other domainer board out there in the WildWildWest.