General question, with lot of answers ....
From a CAD point of view, from a PLM and BOM point of view ...
skeletons, space allocation DMU, Design in Context ...
lot of solutions depending on your needs, and product complexity
second: Take care of the references and dependencies
third: read Perasso's post 😉
Resume: more details please.
Check out the post from Brian Martin about half way down. It even has a pdf file for top down and some files:
Hope this helps.
check this too, it is also good tutorial,old but good http://www.sharptechdesign.com/Tutorials/ProE_Fundamentals_WF2/WF2_Lesson38.htm