So here is the guide to taking a taxi in Cairo. There are basically two options for a taxi: white or black. For the regular tourist, take the white taxis. The white taxis have air conditioning and meters to track your total cost(usually). Black taxis don't have either of the above. Either way, taxi drivers will try to quote you a price for where you want to go. You have the option of haggling them down or asking for the meter (if they have one/or it's working). Unless you know the estimated fare, don't trust the amount they quote you. They WILL rip you off. I've been quoted 30 EGP for a ride I knew only cost 7.50 EGP. Taxis from the airport are the worst. They will quote you 100 EGP or a ride that only costs 25-30 EGP.
If you get into a metered taxi, the meter will run even if you're stuck in traffic (at a reduced rate). Unfortunately, if you don't know the way to your location, you could get a taxi driver who takes you a longer route. The most important thing to remember when dealing with a taxi driver, or anyone for that matter, is be tough. Call them out if you think there going the wrong way or ripping you off.
Just remember, you can always wait until the next taxi. They're everywhere in Cairo, and you will find some really amazing, honest taxi drivers.