Tap water in Shanghai is safe for brushing teeth. However, it contains a high concentration of metals, so you should buy bottled water to drink. It is available at every corner store—look for FamilyMart, Kedi, AllDays, and Watsons—and will cost you between Y1.50 and Y3. Make sure that food has been thoroughly cooked and is served to you fresh and hot; avoid vegetables and fruits that you haven't washed (in bottled or purified water) or peeled yourself. Shanghai's polluted air can bring on, or aggravate, respiratory problems. If you're a sufferer, take the cue from locals, who wear surgical masks or a scarf or bandanna as protection. Masks can be purchased at convenience stores.
The most reliable places to buy prescription medication is the 24-hour pharmacy at the ParkwayHealth Medical Center or the Shanghai United Family Health Center. During the day, the Watson's chain is good for over-the-counter medication, but has limited selection; there are dozens of branches around over town. Chinese pharmacies offer a fuller range of over-the-counter drugs and are usually open later; look for the green cross on a white sign. Pantomiming works well for things like band-aids, ace bandages, and cough medicine, so do not feel embarrassed to use hand gestures.
There is almost no violent crime against tourists in China, partly because the penalties are severe for those who are caught—China's yearly death-sentence tolls run into the thousands. Single women can move about Shanghai with little to no hassle, though as in all major cities, handbag-snatching and pickpocketing do happen in markets and on crowded buses or trains.
Shanghai is full of people looking to make a quick buck. The most common scam involves people persuading you to go with them for a tea ceremony, which is often so pleasant that you don't smell a rat until several hundred dollars appear on your credit-card bill. "Art students" who pressure you into buying work is another common scam. Avoiding such scams is as easy as refusing all unsolicited services—be it from taxi or pedicab drivers, tour guides, or potential "friends." Simply put: if someone is offering you something, you don't want it. It is not considered rude to ignore them.
Shanghai traffic is as manic as it looks, and survival of the fittest (or the biggest) is the main rule. Do not be afraid to cross when the light is red, as you may not have a chance once it's green. Beware of buses, which make wide turns and regularly ignore pedestrians' rights.