you plot to PDF in autocad. open up the PDF in illustrator and then bravo! the lines in the PDF are turned to vectors and are manipulated in illustrator. in it you can change lineweights and such. i'm sure there are plenty of quick tutorials out there to get you started.

dirty trick I learned in college was to just copy in cad and paste in illustrator, it takes a while to clean up the mess and assign strokes in illustrator, but its quick and dirty trick.

you can just open dwg in illustrator, and if you work neat in layers in cad it's easy to select stuff and adjust strokes or filling in. it's also very easy to select lines based on their colour in illustrator to make groups or new layers.

do your color fills w/ live paint-- real snappy.

1. install this: http://kb2.adobe.com/cps/402/kb402977.html

2. save cad file as 2000 dwg

3. open and draw

also, remember to draw closed polylines...or theres always livepaint...