If you set a few ground rules about sharing a refrigerator with roommates, your #apartment will be a much more harmonious place. Check out Apartment Therapy's tips on #SharingAFridge.
Make a decision as a group whether you are going to share food, condiments and beverages and make sure everyone is clear on the rules that are agreed upon. When making the decision to split or not to split, discuss your at-home eating habits. If one person eats all their meals at home while another likes to eat out all the time, splitting 50/50 will not be fair.
If you make the decision to not share, give your roommates a heads up if there is anything of yours you are okay with sharing. Condiments are a great thing to share without too much trouble. However, whoever is the one to use the end of the shared condiment should replace it.
Give everyone equivalent space in the refrigerator. It could be a shelf for each roommate or just a rough estimate of how much space you can use. Even if you keep the limits loose, be courteous and don't buy in bulk at the store.
All housemates should make sure that all food is covered to prevent odors and mold. Make sure to wrap foods that give off a strong smell extra well.
Label all food so it's clear which roommate leftovers belong to, both so no one eats them and so you can hound the appropriate person if something starts to go bad.
Set up a schedule for how often the fridge is cleaned, who does it, and what exactly constitutes "clean". However, if you're the one whose food spills or leaks, clean it up whether it's your turn or not. In addition, get rid of rotten produce weekly.
Follow these rules and you can share a fridge in peace!