Most oasis trips begin in Cairo. If you're driving to Siwa, head toward Alexandria. For the other oases, head toward the Pyramids in Giza. Check that your car is up to the trip, and make sure you have spare parts (especially a working jack), extra gasoline, water for you and the car, maps, guidebooks, and—if available—a good GPS. Always top off your tank when you come across a gas station because they're few and far between.