best import format to produce useable surfaces (stl?)

Ok, so I've had the best luck at importing stl files tosolidworksbut only in the sense that the result is a model whichappears asline item: 'STL graphics' and accurately represents themesh Iintended.  However, the data shown can so far be usedforvisual purposes only.  At best, I can trace over thecontoursand get some generally useful data. My question is whattoolsand/or import options/formats can I specify that will produceamore useful mesh?  I can't seem to do anything with themodeldata that I have other than look at it and guesstimatecontours. I'd like to at least do things like trim withsurface, oroffset surfaces- anything real.  
Thanks for any help!
-kevinSolidworksSurfacing