A fresh loaf of bread is best eaten within two to three days. To save bread so it stays fresh longer, it is advised to store it in a paper bag better than storing in plastic. Because plastic actually encourages mold growth, resulting in the bread to go bad much faster.
And, bread boxes are a great way to keep bread too. They have small holes in them, which allow just a little air to circulate, keeping bread from molding.
If you cannot finish the loaf, or are not going to eat the loaf in two or three days, never keep it in the fridge. The starch molecules in bread recrystallize very quickly at cool temperatures, and causes the bread to stale much faster when refrigerated. You can notice that in bakery shop or supermarket, the loaves are showed in display cabinet at room temperature, not in display refrigerator. So, shop-bought loaves should be kept at room temperature rather than in the fridge. The best option is to freeze it for the longest time possible. Wrap tightly in a freezer bag, either whole or sliced. Defrosting a whole frozen loaf in the refrigerator overnight is the best way, and unwrap it from the freezer bag when defrosting. If you have not so much time to defrost in refrigerator, you can reheat bread straight from the freezer. The reheat temperature and time according the size of loaf or slice.