Requesting records from police departments
The easiest thing to do is call the police department in possession of the records you are seeking. When the phone is answered, say that you'd like to file an open records request and you want to know who at the district handles these matters. You won't be the first person who has called and asked. Normally, the person who answers the phone will immediately be able to tell you the name of the person who is responsible for handling requests.
Check that you have the correct spelling of the person's name. Then, ask what address you should use. It is often but not always the address of the main administrative office.
If you prefer to use email, you can also try searching the website of the police department in question to see if they list contact information for records requests. If they don't, you can try searching on the website for the police chief's name and email address. If you find it, just send the police chief a quick email asking for the procedure for filing an open records request.
Consider noting in your email that you tried unsuccessfully to find this information on the department's website. A polite request that the department update its website to make it easier for citizens to ask for public records will help those who come after you.
Please keep in mind that states often have wide ranging exemptions for police records and complicated rules for records involved in ongoing trials. Please consult your state's law or consider consulting a lawyer when making records requests from police departments.