Eating on the floor, or on a takht (a sort of daybed), is normal here. So if you end up in someone's home, remember to remove your shoes before sitting around the plastic sheet that acts as the 'Iranian table', and avoid putting your left hand into a communal dish.
For Iranians, breakfast is a simple affair, consisting of endless tea served with leftover (ie rather crisp) lavash, feta-style cheese and jam - often carrot-flavoured. Most hotels usually throw in an egg. Lunch is the main meal of the day and is eaten with mountains of rice between noon and 2 pm. Dinner is usually a bit lighter and eaten from about 7 pm onwards. Many restaurants close earlier on Friday. On religious holidays, almost everywhere selling food will shut for the morning at least.