A good first step to securing your WiFi access is to make sure you get a good, enterprise-grade access point and router in place. Then it's time to settle down and secure the APs you've plugged in. That requires some authentication effort -- encryption and adding on some virtual local area networks (VLANs) isn't a bad move either. The next step up are sensors that can evaluate the RF domain for foreign and rogue devices. If unauthorized access is detected, an automatic alert is sent to network administrators.

For more on securing WiFi from thieves:
- read this Networking Pipeline article [1]