Ugh I was going to write up a lot, but it got way too confusing even for me
The short and sweet:
Use primitives to first "sketch" your idea (boxes, spheres, cylinders). Use the objects properties can make things easier down the the road. (like instead of cutting a sphere in half, just use slice On property instead).
Once the rough draft is in place, then go in and use edit polys (edit mesh is ok, edit patch/nurbs I'd stay away from unless your doing organic stuff). Slice plane, chamfer, extrude, insert, bevel...etc until it's looking like what you want (minus the greebling, thats last). If you find yourself extruding an object to create a large new area, I'd suggest using a new object. For example in the tutorial jacek posted, I'd create the wings from a separate box. Couple reasons for this, it's easier to modify one without affecting(effecting?) the other and makes cloning it easier (for example, grillwork). I usually start at one end of the ship and work my way to the other end.
Once this is all done, then greebling/detailing comes into play, which isn't important at this stage yet.
Basically, think of it as woodwork. The first stage your using a electric saw to chop the woodblock into something useable. Then your going to use a hammer and chisel to bring in the details and finally use those sharp carving tools to do the fine details.
I'm assuming your using max, since you mentioned Mental Ray.
I don't really recommend using the Mirror tool, rather use the symmetrical modifier (as in #4 in jacek url). Mirror creates a new separate object, whereas symmetric modifies the existing object thats welded to the original. It keeps things a bit cleaner than mirror as it removes chopped polys and welds the vertices. In the end theres less work to be done. (Also if you convert the model to at least 3ds, you'll end up with flipped normals using mirror)
