At each of the complex ranges, before you set up and start shooting, look for a sign-in station.
At each station, there will (or at least should) be a log book. Sign the log, filling out the required information. This includes information for any guests you have brought.
Why? There are several reasons, but it was initiated by our need to accurately track our membership numbers and usage for our insurance company. In addition we want to make sure that we are complying with our insurance requirements, and not allowing uninsured non-members to utilize our range as guests outside of their one-time visit.
The range usage and numbers are also neccessary to have when we are pursuing grants for range development or maintenance.