The traditional practice of the Church on days of strict fasting (such as Wednesdays and Fridays) is to abstain from food and drink until the Ninth Hour (i.e. 3p.m.), although in practice this usually means abstaining until after Vespers since the two services are normally combined. After this, one is encouraged to just eat a single meal, which should not contain any meat, eggs, dairy, fish, oil or wine.
However, how one fasts is very much a personal matter. Most do not fast as strictly as what I described above, others observe a rule much stricter than what the Church prescribes. You work out, on an individual basis and with the help of your spiritual father, what you are capable of and what will be most beneficial for your spiritual progress.
Fasting from food is only an aid to help us fast from the passions. Our fast should, therefore, also be accompanied by prayer, almsgiving, helping others, etc. Again, the extent to which we do these things is something that should be worked out on a personal basis.