Help Clean Up My Models!

Hey...I (hope) I am at a point in 3d modeling where I can began to concentrate
on making my models CLEANER.  Rather than having a bunch of polygons or NURBS
representing a complex model, I would like to shave down that amount if I
can...Up until now, I have used the Grouping hotkey to manipulate several
primitives as one, yet I would like to fix them together permanently with a
method other than Parenting (particularly NURBS and NURBS blending)...So
basically, how do you Professional 3d Modelers go about modeling as if you were
concerned about programming and space issues (i.e. modeling for a computer game
or animation).  I guess the best way to see this would be to take apart an
actual scene someone made, however I am on P.L.E. (college student heh).