Hi

I am new in Salesforce development. I am creating a simple reference check apps using  force.com sites.
I am done with the VF page. But how can I able to override the save button to do additional things like
go to the thank you page.

I am now catching up with the reading using apex and  some post recommends to create a SF class to do this.
Please give me idea how can I do this. Thanks in advance