A general guide to the fasting discipline of the Church may be found here. Be aware that as with many other things in Orthodoxy, your mileage is going to vary a bit. There are local variations and you can find stricter, more detailed, and more lenient versions of the fasting discipline if you want to look around. But the linked site gives a pretty decent run down of the basics.
It is important though to remember that Lent is not a legalistic test to see how well we can keep a fourth century dietary code. Rather it is a spiritual exercise intended to stretch and temper the body so it does not come to rule the spirit. To which end I'm going to add a few observations and addendums.
- Mind your own business. Your fast is your concern, your neighbor's is not. If you feel the need to brag about how well you are keeping the fast, save it for confession.
- In line with the above, avoid gossip. It is one of the vices most frequently condemned in Scripture yet most prevalent in modern society.
- Be prepared for failure. I have NEVER come close to keeping the Lenten Fast perfectly. Very few outside of monastics do. That is not an excuse to ignore it, but it is an acknowledgment of our human weakness. When you fall, pick yourself up and get back on the horse.
- Shelve the triumphalism. I am seriously sick of the annual commentary about how WE still fast, unlike you know who. Every year those comments are as inevitable as a call of nature, and more or less as pleasant to contemplate.
- Baptism by total immersion is a no no with fasting. If you are new to the Faith, do not attempt the full rigors of the fast. You will fail, probably badly, get discouraged and ultimately surrender. Talk to your spiritual father and get a modified rule from him. For the non-Orthodox looking to try something perhaps a bit more stringent than what they are accustomed to, I suggest Ad Orientem's Lenten Fasting for beginners... no meat throughout Lent and keep a strict fast (one meal only with no meat fish wine oil or dairy) on Wednesdays and Fridays. If you can handle that, you are doing pretty good. The other stuff can come later.
- Common sense is not on the fasting list. If you are at work and feel faint because you are so hungry... don't be a twit, EAT SOMETHING! Likewise legitimate health issues trump the fasting rules. When in doubt consult your doctor and spiritual father.
- Don't play the martyr. If you are making other people miserable because of your fasting either eat something or excuse yourself from the company of others. If someone unknowingly surprises you with a nice meal that's not on the OK list, the correct response is not "sorry I'm fasting." You smile, politely thank them and eat, even though that succulent juicy steak will undoubtedly make you miserable. The basic rule here is if your fasting makes someone else feel really bad then you have failed.