I am developing a website that allows a user to view/enter their banking, credit card and other 'sensitive' information.

I am aware that I have to use HTTPS for communication, but over and above that, I am not sure on what else needs to be done.

I would ideally like to encrypt data sent between the client and the server, but I don't know if this is already done by using the HTTPs protocol.

Any ideas on where to get additional information on best practices for developing such a web application?

Additional info: I will be developing/deploying this website using a LAMP stack.