Every family has its own routines for day-to-day life including what time they generally rise in the morning, when they eat lunch, when they expect the house to be quiet by in the evening, which TV programs they always watch and which days they do the grocery shopping.
Try to get acquainted with the family's routines as soon after your arrival as possible. Nobody will mind you asking questions although it isn't a good idea to bombard the hostess with too many questions at once. Ask the most obvious ones first. Perhaps the children can tell you what TV programs they'll be watching and whether everybody will be going to the ball game tomorrow evening?
Do make sure you know what time the family members are likely to rise. No doubt there will be a rush for the bathroom so try to hang back a while -- you don't want to make a longer queue than necessary. If you can't wait, get up a little earlier than the others and head for the bathroom first. Just make sure you leave it tidy and that you don't occupy it for longer than necessary.
If you're an early riser it's worth informing your host family. Unless you want to become intimately acquainted with a baseball bat, don't let your host think there's an intruder in the house when he hears you wandering about at five-thirty.
If you're not going to be around for a meal, let your hostess know in good time. It's terribly disrespectful to allow your hostess to prepare something special only to have her guest call at the last minute to say they won't be back for the meal.