In (a short) Episode 3, Gill discusses the importance of creating a development process. She covers why it's important to have a clearly defined process, how to set one up, what should be included and what to do when you've been using it for a while.
Here are some example models you might wish to research when designing your own process:
In the episode, she talks to an elearning module from Little Man Project on their development process.
You might also find this post by Laura Shaw on the process they use at Cats Protection helpful.