One way to help children understand the key features of a text type is to pick texts apart and find them themselves.
As part of shared reading sessions and literacy lessons, at the beginning of studying a new genre, we read lots of good quality examples of that text type and investigate it asking the question 'What makes this a ...?' We do this for both fiction and non-fiction text types.
Once we find out what those key features are, we display them on a genre map on our literacy display. The types of features we are looking for are: content, language, organisation/ layout and the purpose and audience. Of course as teachers, all these key features are in our planning before hand so we know exactly what we want the children to find. You could make it a challenge whereby all the key features are already on cards and they have to find all the answers on the cards by the end of the lesson/week.
I also like to display highlighted and annotated copies of texts on the display that we've explored so the children/ myself can refer back to them when learning/ teaching. The children like to magpie ideas from these too.
Here is my genre map display in the making...
As you can see the display is flexible and handwritten as the key features can be found and added at any time - another look at a literacy working wall really!