Share internet with MAC OS X

There are situations we need to share internet connection from one machine, MAC support to share internet
From: Firewire, Ethernet, Airport, Bluetooth To: Firewire or Airport or Bluetooth PAN or Ethernet.

Simply get your mac connected to internet, say with ethernet

Enabled Internet sharing:
System Preference --> Sharing --> Internet Sharing

Select source of connection and mode of sharing
If you share via airport you have options to set encryption to avoid anonymous to use your connection.

Also to make your internet kinda nat’d,
Assign different network ip to the airport interface.

Say :
You are connected to internet with a dhcp ip 192.168.10.6 on ethernet port
Assign a different network ip 10.1.1.1 to the Airport interface and set gateway as 192.168.10.6
Configure 10.1.1.2 with gateway 10.1.1.1 on the client machine.

This way all the connection will be shown as single ip to the provider ;)