While writing, you want to describe the setting, the characters and the action. But do you need to describe the inside of a bathroom? Probably not. Do you need to describe in detail the character brushing his teeth? Not likely. Everyone knows what the inside of a bathroom looks like and what brushing teeth is all about. But you might want to describe the character as he or she looks in the mirror. And even there, not every detail. Just enough to give the reader an idea of age, sex, level of attractiveness, and attitude of the character to themselves.
"If you say in the first chapter that there is a rifle hanging on the wall, in the second or third chapter it absolutely must go off. If it's not going to be fired, it shouldn't be hanging there." - Anton Chekhov
and...
"Good description is a learned skill, one of the prime reasons why you cannot succeed unless you read a lot and write a lot. It's not just a question of how-to, you see; it's also a question of how much to. Reading will help you answer how much, and only reams of writing will help you with the how. You can learn only by doing." - Stephen King, On Writing
Only describe details if they're important to the story. Or in other words, your descriptions should be the length of a girl's skirt: long enough to cover the subject, but short enough to keep it interesting.
