The folks at Cooks Illustrated write in their ever-so-modestly titled tome The Best Vegetable Recipes that the best way to bake sweet potatoes/yams is to lightly coat them in vegetable oil, pierce ‘em multiple times with a knife, and stick them in a 400°F oven for 45 minutes to an hour. 

When I baked some tonight, I coated my tubers with melted coconut oil instead of vegetable oil before popping them in my oven.

Voila!  Perfect baked sweet potatoes — creamy flesh and dry, crispy skin. Not too shabby for 5 minutes of hands-on time.  Don’t wrap your tubers in foil before you bake them, people!