Hi Anthony,
you take a cutting from under a "node" which is the "bump" just under a leaf and the base of its stem (where leaf connects to main stem). For pothos I usually take a cutting below the 3rd or 4th leaf, strip off the bottom leaf and then stick it in a clear glass of water. Not every plant can be propagated in water but pothos will form roots quickly.
Some tips:
- keep the glass out of direct sun or algae will quickly form
- change the water regularly
- once it has rooted some of the roots may get sort of slimy but you can just pull off the slime (if you change water this will happen less)
- don't put any plant food in the water
- you can maintain a plant this way for a very long time but it can have a harder adjustment to soil the longer you keep it in water so I would pot it up after you have a healthy root system (like before the slime 
See the link which shows where to take a cutting
as for training it I assume you mean have it wind around stuff? Don't even bother. it will find its way around the cage interior all by itself 
Hope this helps!
lele
cuttings