I wash them, pierce them on all sides with a corn holder, and cook them for about 4 minutes for each potato. BE SURE TO PIERCE THEM or they can explode!
So if I'm cooking 2 potatoes, I cook them for 4 minutes on high , turn them over, and cook for another 4 minutes on high.
You can pierce them with a skewer (or fork) to see if they are done. If they are not soft all the way through, cook for another minute and test again.
Sometimes I'll cook them part way in the microwave and finish them up in the toaster oven for about 1/2 hour at 400 degrees.
The microwave is great when you're short on time, or forgot to start them early enough.
Judy