1) Don't use TCP/IP for File and Printer sharing!
Access Points are usually installed on your LAN, behind any router or firewall you may be using. 

2) Follow secure file-sharing practices

3) Enable WEP Encryption

4) Use WEP for data and Authentication
Some products allow you to separately set the Authentication method to "Shared Key" or "Open System"

5) Use non-obvious WEP keys and periodically change them

6) Secure your wireless router / Access Point (AP)
Your router or Access Point should require a password to access its Admin

7) Disallow router/ AP administration via wireless

8) Use MAC address based Access and Association control

9) Don't send the ESSID

10) Don't accept "ANY" ESSID
The "closed network" feature also won't accept connections from clients using the default "ANY" ESSID....

11) Use VPN
This is the most secure route to your data.

If you have any particular requirements then please contact us and see what we can do for you.