"A refrigerator is fine, but it's not great for long-term storage. I wouldn't keep it in there for more than a few months. Your fridge is colder than most wine storage facilities; 50 degrees is the sweet spot for Champagne. If you want to bring a bottle to someone's house and drink it that night, fill a bucket a third of the way with ice then top it with water. Put the bottle in there, and in about 20 minutes, it should be good to go.
"Light will also damage Champagne. The refrigerator light won't do a whole lot of damage, but sunlight will. If you want to keep a bottle for, say, a year but you don't have a wine fridge, find the coolest spot in your apartment and keep it there. Be sure that the temperature is consistent, though. One of the biggest enemies is a huge swing in temperature. You don't want it to get very hot and very cold, and then very hot and very cold. Whoever designed the rack for wine storage that went over the oven, they weren't helping."