How do I reduce balsamic vinegar?

I suggest not using an expensive balsamic but rather a less expensive one as the reduction will be easier on the pocketbook and taste the same.

make sure to keep it on a low simmer so you don't scorch it - I usually reduce by half to 1/3 depending how thick I want it

Easy: just put it in a pan and let it boil down to the consistency you want. By "reducing," all you are doing is evaporating the water in the vinegar, thus concentrating the flavors and thickening the texture.