To make an appointment for visa extension, renewal and reissue, you could visit the official website of Public Security Bureau of Shenzhen Municipality, specifically as the following:

Visa extension:

//msjw.ga.sz.gov.cn/crj/crjmsjw/wsyy/ajax/msjwsxMenu.html?ywpid=000100

Visa renewal:

//msjw.ga.sz.gov.cn/crj/crjmsjw/wsyy/ajax/msjwsxMenu.html?ywpid=000200

Visa reissue:

//msjw.ga.sz.gov.cn/crj/crjmsjw/wsyy/ajax/msjwsxMenu.html?ywpid=000300

(Just click on the links above for the corresponding services)