You'll find a lot of tips in this thread.

http://moi3d.com/forum/messages.php?webtag=MOI&msg=2036.1

Personally I think until MoI has more surface to surface tangency options, aircraft and cars will always be quite difficult and probably best modelled in sub'd with a poly modeller.

The Abarth thread is good also for some tips on rebuilding curves and surfaces and still maintaining tangency
http://moi3d.com/forum/messages.php?webtag=MOI&msg=5601.1


Excellent tutorials here also by Mike Maynard
http://www.k4icy.com/tutorials.html