@Waylen Herdman I'm not sure that there are particular zip codes you should focus on in Clarksville as every one of our zip codes has good and bad areas, in my opinion. Of course, everybody's determination of "good" and "bad" areas/properties is subjective and will vary. If you come across a particular property you are interested in (or would like a list or to be set up on auto-notify alerts) and want my opinion on if it is an A, B, or C area I'd be happy to help.
When I'm working with an investor or doing research for my own investing I look at every property on an individual basis paying attention to proximity to employment for whatever the target tenant base is. e.g. Military/Contractors at Ft. Campbell, APSU, companies located in the Industrial Park, Tennova, etc. I also like properties located conveniently to Wilma Rudolph Blvd., Tiny Town Rd., or Madison St. as those are main roads for shopping and restaurants.
One last suggestion would be to cross-check any address you are interested in against the crime data. I like to use CrimeReports.com.
Hope that helps!