There are several different types of parking lots, this being the main kind that use tokens. Others may take a picture of your license plate as you enter the parking garage and then when you get ready to exit you will type the first few digits of your plate number into the machine, it will then pull up a set of pictures for you to match your vehicle and allow you to select the correct car. After paying, just pull up to the exit and the system will recognize your vehicle and allow you to leave. There are also lots that use cards rather than tokens, it’s the same principle, just put the card into the slot in order to pay out.
There are a few lots in Taichung that will allow you to use an EasyCard to pay, this is quite common in Taipei, but hasn’t made it to Taichung quite yet. I’m hoping this becomes the standard island wide as it makes things very easy.
Also, remember that many lots (including the department stores) have a relationship with stores and restaurants nearby. So take that token with you and ask if they validate – you can get some time for free based upon how much you spend.