Preventing man-in-the-middle attacks on wireless networks

This book has some information on preventing man-in-the middle attacks on wireless networks.

Specifically:

Static ARP Entries
To protect against ARP man-in-the-middle attacks, which are described in
Chapter 2, set static ARP entries using a startup item script similar to the one
described for the firewall.

It goes on to explain how to do this.

Man-In-The-Middle on Wireless Networks