Here is a great tip for storing potatoes from myrecipes.com. This is some really good information. Enjoy!

How Do You Know When a Potato Is Past Its Prime?
Good potatoes are firm, smooth, and sprout-free.

You can tell a potato is spoiled when it is:
Growing mold
Sprouts, or “eyes,” are an indication that your potato is reaching the end of its life. However, they’re not harmful and can be simply removed before cooking. As long as the potato looks, smells, and feels right, sprouts are no biggie.

How to Store Potatoes
1. Keep them in a cool place…
Raw potatoes will thrive in a cool, dark place. The ideal temperature range is 43-50°, which is slightly above refrigerator temp. During cooler months, storing potatoes in an unheated basement or an insulated shed is a great idea. It’s a bit tougher to store potatoes in the summertime, but use your common sense—instead of putting them next to a window, keep them in the area of your house that stays the coolest.
2. …but not the fridge.
Raw potatoes like to be cool, but not cold. Very low temperatures can actually change the flavor of your spuds and make them dangerous. This “cold-induced sweetening” happens when the starch is converted to reducing sugars, which can form cancer-causing substances when cooked.
3. Avoid areas with lots of light.
Exposure to light can cause your potatoes to produce chlorophyll and turn prematurely green.
While this color change is usually harmless, excessive sunlight can also cause potatoes to produce a toxic chemical called solanine. Ingesting solanine in high amounts can cause unpleasant side effects like nausea, diarrhea, and vomiting.
4. Don’t wash them before you put them away.
Step away from the sink! It’s best to keep potatoes as dry as possible if you’re trying to make them last. Moisture promotes the growth of fungus and bacteria—so wait to wash them until right before you use them.
5. Let them breathe.
Prevent moisture accumulation by allowing your potatoes plenty of airflow. If you store them in a tightly sealed container (like a ziploc bag), the moisture released by the potatoes will have nowhere to go. Your best bet is an open bowl or paper bag.

Bonus tip: Don’t store your potatoes with your onions! The chemical reaction will actually cause both to spoil faster. Crazy right?