The stories of people going blind and all that are what weaze said. These troubles start in the fermentation. It comes from putting whatever into the mash to raise the alcohol level. Dont want any wood in there. There are several different easy tests to test for methanol. If you have healthy fermentation it is very hard to make methanol. It has nothing to do with the distillation really.
I'm no distiller, but I think I've read the methanol is a product of the distilling process. I think you're supposed to toss the first runnings (heads) because it contains methanol, collect the middle runnings, and toss the final runnings (tails) because it contains the higher alcohols (nasty tasting fusels). You'll get methanol from corn squeezin's, cane sugar, malted barley...whatever you're fermentng and distilling.