Here is a link to welding instruction for building race car chassis. These principles are applicable for all the cool stuff we make. Look closely and you can see the patterns they use on the MIG guns as well as other tips for using jigs and for welding complex stuff.
http://www.millerwelds.com/resources/articles/How-to-tips-for-stock-car-MIG-and-TIG-welding/
http://www.millerwelds.com/resources/articles/How-to-tips-for-stock-car-MIG-and-TIG-welding/