It is highly advisable not to drink tap water or place ice cubes in your drink. It also may serve you well to bring iodine tablets to put in filtered water. Also, it may be safe to stay away from dairy products unless you know they have been pasteurized.
Moreover, clean your hands with soap and water often so as not to retain bacteria. Public bathrooms usually don't carry toilet paper, so make sure to carry some with you in your bag at all times.
Also, do not ever think of swimming in the Nile. The Nile has dangerous parasites called schistosomiasis, which are tiny bilharzias worms that dig into your skin and breed in your blood vessels, abdomen, and liver and eventually could lead to death. Also, be careful not to walk barefoot in muddy or wet areas.
If anything mild concerning your health should occur, visit a local pharmacy. Pharmacists in Cairo are usually well-trained and speak English and would be a good place to go if you experience any minor symptoms or health encounters. Even if the health concern is serious, these pharmacists could recommend a doctor for you to visit.
Medicine is fairly easy to obtain in Egypt, so if you forget a prescription at home it would not be a problem to get here. Just make sure you know the active ingredient.
If you want to smoke shisha be aware that at certain cafes the pipe is used by many and rarely cleaned. Therefore, for sanitary purposes it is best to smoke shisha out of disposable spouts (these are not totally sanitary, but better off than the shared ones).
