Need help setting up and configuring rsync

Hello

I need help setting up, or rather configuring rsync to sync data between my brand new iMac and my Macbook Air.

Here is what I would like to:

- I want all of the files on both machines to be an exact mirror or copy of each other. Basically I have an iMac for at home, and then a Macbook Air for the road.

- The main folder on both Macs is called 'Sara' and I want the contents (mainly the 'movies' folder, 'music' folder, 'documents' folder and 'pictures' folder) to immediately sync up with each other when both of them are on my home network.

- this means if I'm working on a file at home on my Macbook, it will immediately write to the same directory on my iMac and vice versa (if I'm working on file(s) on my iMac, it will immediately save the contents to my Macbook). This way, if I'm working on last minute project my iMac, and then have to head out the door to the airport, the file is immediately saved to my Macbook (no usb for USB transfer).

- hopefully this makes sense??

Any help is greatly appreciated!

Thanks