If a person doesn't have a root cellar, or basement, buy the dirty potatoes, make a light proof wooden box, and keep it on the cool floor of the pantry/basement?
We also use a lot of sweet potatoes. IMO, they keep longer, have more food value, and are the easiest to microwave. Make sure to stab them with a fork before you nuke them (4 min on each side) to let the steam out - I have exploded a few.
A little fresh butter, brown sugar, cinnamon, chopped nuts, and miniature marshmallows makes for a great sweet potato topping!
I used a dark part of my basement and milk crates. Put newspaper between layers of potatoes and cover the whole crate with burlap. Be sure to pop off any buds when they appear.