Answer: These plants tend to like a rich and moist soil when they are growing outside, but they also need heat to grow well. I suspect that a warmer soil temperature of at least 75 degrees would help -- think "tropical".
You might also start them in a relatively sterile soilless potting mix which provides good moisture holding ability as well as good aeration.
Since these came from the grocery store rather than as ornamental stock, I suppose there is also a possibility that they carried a pathogen or introduced a soil based problem that caused them to rot. To try to avoid that, make sure your tools, pots and the tubers are cleaned with a bleach solution. Use roughly one part household chlorine bleach to nine parts water, soak five minutes and air dry.
Finally, it is also possible that the taro from the grocery has not been handled in such a way to optimize their viability as plants, or they may have been treated to prevent sprouting. You might consider purchasing them from a garden supplier to avoid those possibilities.
With regard to right side up and down, it is nearly impossible to tell with some of them and they seem to grow just fine anyway in my experience.
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