The Range

Your Launch Range must be set up in accordance with rocketry safety rules. These guidelines require that you maintain a Minimum Safe Distance between spectators and the launch positions. The range must also be set up at a location that provides sufficient area to launch and recover rockets at a safe distance from active roads and occupied structures.

This may sound complicated, but if you are working with C motors or smaller, a soccer field will likely serve just fine. Here your chief concerns are trees and power lines.

This website provides basic instruction on how to conduct a launch site Survey.