Best Software Process for our Workflow

Me and another programmer are attempting to set up a collaborative project online. One will be developing the front end part of the website (HTML/JavaScript) and another will be developing the back end (PHP Laravel / JavaScript / MySql).

The question I am asking is which software development process model should we use for a collaborative project between two developers online.

We are using git Github to collaboratively work on the project.

Also we need to find a way of communicating over something more than email to develop the application itself. Could anyone recommend a software or tool we could use.