Minimum Hardware: 
Cpu : PII 500 (first user)
Add +166 (second user)
Add +50 (next 5 users)
Hdd: 1Gb
Mem: 64 Mbs

Compatibility: All but Net Sitter.

Note: Behalf works right out of the box. Unless security is not an issue, you should configure it so that only your Lan IP addresses should be allowed to use Behalf. Remove the 'allow 0.0.0.0/0.0.0.0' subnet and add your own Lan IP/subnet. Especially if Behalf is installed with Gateway.

There are three ways to install Behalf. 

1:
Building your box with Gateway + barbwire + Behalf on the same box. Get the details here.

2:
Installing Behalf on a standalone server.
Get the details here.

3:
You will need to go to every workstations on your network and configure the web browsers to point to the Behalf device.
Internet Explorer:
Click Tools/internet options/connections/lan settings. In Proxy server box, check 'Use proxy server for your LAN' and type the IP address of the Behalf server. Also type in the port on which Behalf is listening. The default port is 3128.

Behalf's default HTTP port is 3128. Many people run their cache servers on a port which is easier to remember: something like 80 or 8080).

If you wish, you can use multiple ports appending a second port number to the http port variable. Here is an example: http 3128 8080