Have a valid unexpired visa in hand. Otherwise, you would not be renewing for a visa, but instead applying for a visa. If granted in Shanghai, a tourist (L) visa can only be renewed twice for 30 days each, allowing you 90 days in the country total. If granted in the U.S., it is possible to get a 60-day renewal, while some countries do not allow the renewal of Chinese visas. Contact your local embassy or consulate to find out for sure.
Gather your passport, one photo-sized photo and a photocopy of the pink registration you got at the police station when you entered China. At the office, be prepared to wait several hours.
Be prepared to wait three to seven days for the processing of your renewal. In China, this may entail making travel accommodations to, from and in Hong Kong or Shanghai. The wait at pickup should not be as long--most likely, 30 minutes to an hour. At the Shanghai office, there is the option of picking up the visa in person or having it delivered to your home or office for a fee.
Bring an extra photo when taking your renewal forms to the offices if renewing in Hong Kong or Shanghai. With this, officials will provide an official temporary passport for traveling the week without your passport.
Bring any proof of travel accommodations for your trip, especially your flight info, just in case. Officials will want to know that you don't plan to stay beyond the time limit you are allowed.
