To the cook, sweet potatoes are easier than pie.
They can simply be scrubbed, poked with a fork in a few places, and baked at 400°F for 35 minutes to one hour, until they give a bit when you squeeze them in your pot-holder-protected hand.
In the microwave, a whole sweet potato baked on high should be ready in 4 to 6 minutes. It may still feel firm when done; let it stand 5 minutes to soften.
Sweet potatoes can also be steamed whole, cleaned and unpeeled, for about 40 minutes or until tender, or cooked whole, cleaned and unpeeled, in boiling salted water for about 35 minutes. (Boiling reduces the flavor considerably.)
Immerse cut raw sweet potatoes in water until you're ready to cook them; they will darken otherwise.
As a general rule, don't substitute sweet potatoes for regular potatoes in recipes; the two aren't related. Sweet potatoes don't hold together the way potatoes do, and their strong flavor can overwhelm a dish meant for a milder potato taste. But they make a fine substitute for pumpkin, especially in desserts.