I can't speak for everyone as all have thier own methods, but I usually start from a cube, then size and scale it and start extruding until I end up with a basic form of what I am modeling.
The next step is start adding a little detail using split polygon tool or edge loops to gradually refine it until you get the amount of detail needed for you to be satisfied with the model.
Don't forget you might not need to model every single little thing on your model because some things can be achieved by either using a bump map, displacement map or even just the texture if it's not going to be seen up close.
The bottom line though is there is no right way or wrong way to go about modeling, it's simply what workflow you yourself feel most comfortable with.

A few basic rules need to be kept like trying to stick to 4 sided polygons as much as possible will help with texturing and animation but if you model is simply a static render then this is not so much a worry.

Try not to use n gons (polys with 5 or more sides) but a few 3 sided would probably not hurt here and there.