If you have a specific reason to avoid using your visa (for example you only have a single or double entry visa, and you wish to 'save' these for a later trip), you can still use TWOV. You need to make it clear to the immigration agent on arrival that you do not want to use your visa (for example, carry a printout of the TWOV page in Chinese, and have the 'TWOV' circled).

If you have a multi-entry visa, just use your visa.