During Lent observant Orthodox Christians will adhere to a fasting regimen that is often quite intimidating to the newcomer or inquirer. This can be especially true for those coming from a Western Christian background where fasting has largely faded as a discipline. It should be noted however that many (probably most) people outside of monastics do not keep the fast according to the strict letter of the law. Fasting is not intended as an exercise in legalism and should not be approached in that vein. Rather it is intended as a spiritual exercise designed to strengthen the soul by depriving the body of the comforts it is used to and thereby better preparing us for the spiritual warfare we all must face. It is also intended as a means of aiding the poor since money saved through fasting is supposed to be given as alms. The bottom line is that everyone's fast is a private matter and in fact it's considered rather bad form in Orthodoxy to ask other people how they are keeping the fast or to discuss yours since we all have different situations and circumstances in our lives. Also scripture is very clear in warning against the false pride of those who wear their fasting on their sleeve so to speak.
The exception to the above rule is of course one's spiritual father / confessor who should be kept informed of how your doing and consulted if you think any major changes need to be made in your fast. This is NOT however the same thing as telling him you broke down and had a cheeseburger on the 3rd Tuesday in Lent. For most of us its a given that there will be moments of weakness and such details are usually gratuitous unless the weakness is habitual. If we fall, get back up. And again it bears repeating that fasting is spiritual medicine not an exercise to see how well you can follow a monastic discipline. As the Fathers were oft want to note, the devil and his demons do not eat or drink either. Again, there are some minor differences for those following the Western Rite. The discipline employed by the Antiochian Archdiocese for the WR can be found here (pdf). That said, the fasting guidelines for most Orthodox are below.
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 (again very few lay persons follow this strictly). 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, but more typically after Holy Communion at 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. Fasting is relaxed or dispensed as the situation warrants for the very young, the very old and the sick as also for those who travel or whose work requires them to eat. Also it is a general rule that if one is a guest and the host serves food or drink that violates the fast one should not do anything which might cause embarrassment to the host or draw attention to your fasting. In short eat or drink what is offered to you. The above rules are the strict monastic rules which should be followed to the extent reasonably possible. However, as with so many things in life, your mileage will vary. The advice and council of one's confessor should be sought where there may be questions.
In closing I wish to ask pardon from anyone who I may have offended or hurt through any word, action or neglect on my part. Please forgive me.
Under the mercy,
John / Ad Orientem