The following is borrowed from here and I posted it as a general help to Orthodox and non-Orthodox seeking to understand the general fasting rules and seasons.
Keep in mind that the Church has expressed Herself in various ways in different cultures in various times so slight to greater variations may exist depending if you are Antiochian Orthodox, Russian Orthodox, Greek Orthodox,etc. To further complicate matters, there is the "Old Calendar/New Calendar" controversy. This link will give some interseting research material for anyone wishing to pursue the matter further.
Hope the following is of some help:
The Fasting Rule
of the Orthodox Church
The Church's traditional teaching on fasting is not widely known or followed in our day. For those Orthodox Christians who are seeking to keep a more disciplined fast, the following information may be helpful.
Though the rules may appear quite strict to those who have not seen them before, they were developed with all of the faithful, not only monks, in mind. (Monks do not eat meat, so rules regarding the eating of meat cannot have been written with them in mind. Similarly rules regarding marital abstinence apply only to the laity and married clergy.) Though few laymen are able to keep the rule in its fullness, it seems best to present it mostly without judgement of what level is "appropriate" for the laity, since this is a matter best worked out in each Christian's own setting, under the guidance of his spiritual fathers.
There are many exceptions to the broad rules given here, such as when a major feast day, or the patronal feast of a parish, falls during a fasting period. Consult your priest and your parish calendar for details. The St. John of Kronstadt Press publishes wall and pocket calendars that give the fasting rule for every day of the year. The Saint Herman Calendar, published annually by St. Herman of Alaska Press, is also a good day-by-day guide.
Non-fasting PeriodsFor the Christian, all foods are clean. When no fast is prescribed, there are no forbidden foods.
Weekly FastUnless a fast-free period has been declared, Orthodox Christians are to keep a strict fast every Wednesday and Friday. The following foods are avoided:Meat, including poultry, and any meat products such as lard and meat broth.Fish (meaning fish with backbones; shellfish are permitted).Eggs and dairy products (milk, butter, cheese, etc.)Olive oil. A literal interpretation of the rule forbids only olive oil. Especially where olive oil is not a major part of the diet, the rule is sometimes taken to include all vegetable oils, as well as oil products such as margarine.Wine and other alcoholic drink. In the Slavic tradition, beer is often permitted on fast days.
How Much?Sad to say, it is easy to keep the letter of the fasting rule and still practice gluttony. When fasting, we should eat simply and modestly. Monastics eat only one full meal a day on strict fast days, two meals on "Wine and oil" days (see below). Laymen are not usually encouraged to limit meals in this way: consult your priest.
ExceptionsThe Church has always exempted small children, the sick, the very old, and pregnant and nursing mothers from strict fasting. While people in these groups should not seriously restrict the amount that they eat, no harm will come from doing without some foods on two days out of the week — simply eat enough of the permitted foods. Exceptions to the fast based on medical necessity (as with diabetes) are always allowed.
Communion FastSo that the Body and Blood of our Lord may be the first thing to pass our lips on the day of communion, we abstain from all food and drink from the time that we retire (or midnight, whichever comes first) the night before. Married couples should abstain from sexual relations the night before communion. When communion is in the evening, as with Presanctified Liturgies during Lent, this fast should if possible be extended throughout the day until after communion. For those who cannot keep this discipline, a total fast beginning at noon is sometimes prescribed.
The Lenten FastGreat Lent is the longest and strictest fasting season of the year.
Week before Lent ("Cheesefare Week"): Meat and other animal products are prohibited, but eggs and dairy products are permitted, even on Wednesday and Friday.
First Week of Lent: Only two full meals are eaten during the first five days, on Wednesday and Friday after the Presanctified Liturgy. Nothing is eaten from Monday morning until Wednesday evening, the longest time without food in the Church year. (Few laymen keep these rules in their fullness). For the Wednesday and Friday meals, as for all weekdays in Lent, meat and animal products, fish, dairy products, wine and oil are avoided. On Saturday of the first week, the usual rule for Lenten Saturdays begins (see below).
Weekdays in the Second through Sixth Weeks: The strict fasting rule is kept every day: avoidance of meat, meat products, fish, eggs, dairy, wine and oil.
Saturdays and Sundays in the Second through Sixth Weeks: Wine and oil are permitted; otherwise the strict fasting rule is kept.
Holy Week: The Thursday evening meal is ideally the last meal taken until Pascha. At this meal, wine and oil are permitted. The Fast of Great and Holy Friday is the strictest fast day of the year: even those who have not kept a strict Lenten fast are strongly urged not to eat on this day. After St. Basil's Liturgy on Holy Saturday, a little wine and fruit may be taken for sustenance. The fast is sometimes broken on Saturday night after Resurrection Matins, or, at the latest, after the Divine Liturgy on Pascha.
Wine and oil are permitted on several feast days if they fall on a weekday during Lent. Consult your parish calendar. On Annunciation and Palm Sunday, fish is also permitted.
Apostles' FastThe rule for this variable-length fast is more lenient than for Great Lent.Monday, Wednesday, Friday: Strict fast.Tuesday, Thursday: Oil and wine permitted.Saturday, Sunday: Fish, oil and wine permitted.This is the rule kept by many monasteries during non-fasting seasons.
Dormition FastFasting during the two-week Dormition fast is like that during most of Great Lent:Monday-Friday: Strict fast.Saturday and Sunday: Wine and oil permitted.
Nativity Fast.During the early part of the fast, the rule is identical to that of the Apostles' Fast. During the latter part of the fast, fish is no longer eaten on Saturdays or Sundays. In different traditions, this heightening of the fast may be for either the last week or the last two weeks.
Other FastsThe Eve of Theophany, the Exaltation of the Cross and the Beheading of John the Baptist are fast days, with wine and oil allowed.
Fast-free PeriodsComplementing the four fasting seasons of the Church are four fast-free weeks:Nativity to Eve of Theophany.Week following the Sunday of the Publican and Pharisee.Bright Week — the week after Pascha.Trinity Week — the week after Pentecost, ending with All Saints Sunday.
The Marital FastMarried couples are expected to abstain from sexual relations throughout the Church's four fasting seasons, as well as on the weekly Wednesday and Friday fasts. (This aspect of the fasting rule is probably even more widely ignored, and more difficult for many, than those relating to food. In recognition of this, some sources advocate a more modest, minimal rule: couples should abstain from sexual relations before receiving Holy Communion and throughout Holy Week.)
Health ConcernsDuring fasting seasons, avoiding prohibited foods poses no health risk as long as adequate amounts of other foods are taken. Calcium intake and adequate calories may be a concern for growing children and pregnant and nursing mothers. Calcium-fortified orange juice is an easy way to guarantee plentiful calcium intake while avoiding dairy products. Nuts and nut butters are a good source of calories for those who need to maintain weight on a Lenten diet. If you are new to fasting, you may find the onset of hunger pangs distressing. Hunger pangs are not harmful; they are simply part of the fast. The first few days of a long fasting period are often the most difficult. Do not be discouraged by headaches, fatigue, etc. at the beginning of a fasting season — they will disappear or reduce in intensity. If you are troubled by lethargy, try moderate exercise. A short walk can make a surprising difference in your energy.
At the Grocery Store. Read the ingredient lists on processed and packaged foods. Butter, milk solids, whey, meat broth and lard are common additives.
If you are baffled by what to cook during the fast, consult any of the many vegetarian cookbooks now available in bookstores or your public library. Several good "Lenten cookbooks" are on the market.
The rules given here are of course only one part, the most external part, of a true fast, which will include increased prayer and other spiritual disciplines, and may include resolutions to set aside other aspects of our day-to-day life (such as caffeine or television), or to take up practices such as visiting the sick.
Obviously, many Orthodox do not keep the traditional rule. If you adopt it, beware of pride, and pay no attention to anyone's fast but your own. As one monastic put it, we must "keep our eyes on our own plates."
Do not substitute the notion of "deciding what to give up for Lent" for the rule that the Church has given us. First, keep the Church's fasting rule as well as you are able, then decide on additional disciplines, in consultation with your priest.
We are always advised to fast according to our strength, and you may find from experience that you need to modify the fasting rule to fit your own strength and situation. But do not assume beforehand that the rule is too difficult for you. The Lord is our strength, and can uphold us in marvelous and unforseen ways.
Those who attempt to keep the Church's traditional fast will find that, though the temptations to pride and legalism are real, the spiritual benefits are great. A return to more diligent fasting could play a large part in the spiritual renewal of our Orthodox churches.
Sayings on Fasting
St Symeon the New Theologian:'Let each one of us keep in mind the benefit of fasting... For this healer of our souls is effective, in the case of one to quieten the fevers and impulses of the flesh, in another to assuage bad temper, in yet another to drive away sleep, in another to stir up zeal, and in yet another to restore purity of mind and to set him free from evil thoughts. In one it will control his unbridled tongue and, as it were by a bit, restrain it by the fear of God and prevent it from uttering idle and corrupt words. In another it will invisibly guard his eyes and fix them on high instead of allowing them to roam hither and thither, and thus cause him to look on himself and teach him to be mindful of his own faults and shortcomings. Fasting gradually disperses and drives away spiritual darkness and the veil of sin that lies on the soul, just as the sun dispels the mist. Fasting enables us spiritually to see that spiritual air in which Christ, the Sun who knows no setting, does not rise, but shines without ceasing. Fasting, aided by vigil, penetrates and softens hardness of heart. where once were the vapors of drunkenness it causes fountains of compunction to spring forth. I beseech you, brethren, let each of us strive that this may happen in us! Once this happens we shall readily, with God's help, cleave through the whole sea of passions and pass through the waves of the temptations inflicted by the cruel tyrant, and so come to anchor in the port of impassibility. 'My brethren, it is not possible for these things to come about in one day or one week! They will take much time, labor, and pain, in accordance with each man's attitude and willingness, according to the measure of faith and one's contempt for the objects of sight and thought. In addition, it is also in accordance with the fervor of his ceaseless penitence and its constant working in the secret chamber of his heart that this is accomplished more quickly or more slowly by the gift and grace of God. But without fasting no one was ever able to achieve any of these virtues or any others, for fasting is the beginning and foundation of every spiritual activity'. — Symeon the New Theologian: the Discourses, pub. Paulist Press. pp. 168-169.
Mother Gavrilia of blessed memory spent much time traveling in the service of Christ to places that separated her from the daily liturgical life of the Church. Especially during these times, the advice of her spiritual father Archimandrite Lazarus Moore stood her in good stead: 'Fasting is one of our greatest weapons against the Evil One. I will repeat what Father Lazarus told me once. In 1962, I went to the USA. I stayed there a long time and travelled to many states. The letters of Father Lazarus were a great help... He used to say: "Go anywhere you like, do whatever you like, as long as you observe Fasting"... Because not a single arrow of the Evil One can reach you when you fast. Never.' — Ascetic of Love, the biography of Mother Gavrilia, pub. Series Talanto. pg. 200.
St Seraphim of Sarov on Fasting: 'Once there came to him a mother who was concerned about how she might arrange the best possible marriage for her young daughter. When she came to Saint Seraphim for advice, he said to her: "Before all else, ensure that he, whom you daughter chooses as her companion for life, keeps the fasts. If he does not, then he is not a Christian, whatever he may consider himself to be."' — From a sermon of Metropolitan Philaret, quoted in The Ladder of Divine Ascent, pub. Holy Trinity Monastery, pg.xxxiii.
Abba Daniel of Sketis: 'In proportion as the body grows fat, so does the soul wither away.'