Are you wanting only the police side of all the information? If so, you file the request directly with the police department. Generally send the letter directly to the Chief and they will forward it to the proper authority in their department to handle the request.
You need to be exact and specific on what you are looking for. If you want cruiser video, specify that. You can't make a general statement "all documents and information related to arrest of John Smith." That will most likely be denied as it's too vague (I know it's not, but they are legally allowed to deny that.)
Specify if you want to preview the documents or if you just want to pick it up.
As for getting the actual items, they can only charge you the exact costs. If you request it mailed, they can charge you postage. If you pick them up, it's actual costs of the paper and any media format for the audio/video.
Personally, in the 21st century, I like to make requests via email and ask for all items to be emailed back if possible, and if they can't be due to size limit for that to be specified for each item and those items to be put on a CD/DVD. Why? Well, unless they got really smart, it's hard to figure out the costs of scanning and converting to a PDF and emailing a video/audio file. They can't charge you for the time it took.
Check out the manual above and send off a request.