Start up a chimney of charcoal and allow it to get white ash on the coals.
Once there is white ash on the coals, pour the coals out onto one side of your grill.
Place the sweet potatoes directly on top of the coals.
After about 15 minutes rotate the potatoes by 1/3 of a turn.
After another 15 minutes rotate the potatoes by another 1/3 of a turn. At this point the outside of the potato should be completely blackened. Don't worry, only the outside of the potato gets charred.
At around 45 minutes the potatoes should be fork tender. Remove and serve.
I find that it is best to carve off a one inch strip of the charred skin and then split it open from there. Top each sweet potato with 2 tbs of butter, 3 tbs brown sugar and a pinch of chili powder.
You can just split the sweet potatoes but some people believe that the charred skin skewers the flavor. However, Dana and I love hints of the charred skin in the potato.