Most TSA regulations, policies, and procedures are aimed at air carriers and commerical operators. They have parameters that drive what level of security must be employed. At most GA airports, that aren't serviced by a part 135 carrier, the requirements are IMO pretty transparent to the average renter or aircraft owner. In my experience that means some kind of Airport issued ID. Once you get above 12,500 lbs aircraft GW, the security requirements begin to grow. Of course, the Airport Management and airport businesses (like FBOs) always have more to deal with and its exponential based upon airport population and number/type of operations.

Here's a website with lots more info:

http://www.tsa.gov/stakeholders/subc...ation-security