Depending on how you are travelling - ie if you are in a resort, or if in Cairo / Luxor etc making your own way: you get a much more westernised outlook in resort hotels but even in these I would avoid eating salads, and only eat fruit you have peeled. As above, bottled water or soft drinks.
As a woman especially not accompanied by a man outside resort hotels, you must take responsibilty for yourself and dress in the knowledge that Egyptian men appear turned on by the sight of an ankle. You really do need to cover up - I don't mean going to extremes but a calf-length or longer skirt and a top that shows no cleavage and is elbow length will give out safer messages that 'normal' western clothes. Trousers are fine, but as loos can be a bit dodgy outside the resorts, a skirt makes it easier to manage a p.
Wearing dark sunglasses also helps 'cut off'' predatory male attention. keep a pashmina or similar handy for covering head / shoulders as this too can help give out a certain message.
The further you go from Cairo, the more conservatively women dress and so again it all depends on where you are going.
Taxis are a notorious rip-off. Your hotels may have some favourite drivers if you ask. If you need to stop a street taxi agree a price before you get in. They are very cheap but it is not unknown for a driver to start demanding exorbitant amounts if they are evil and sense vulnerability. Most Egyptians are lovely honest people but as a lone woman tourist you have to protect yourself if only with knowledge in advance.
I would take as few valuables as possible - my own practice is to keep my passport on my person in a secure body belt all the time, and any handbags of the sort that can hang right across your body rather than on one shoulder.