We often think of written mode texts as being formal, largely because they tend to be planned, permanent and non-interactive. Make sure your analysis is more subtle and specific than this.
Things to particularly consider about written texts include:
- How graphology is manipulated for effect
- How the audience is positioned (what assumptions are made about who will read this text)
- The level of formality and specificity of the lexis
- What devices the text uses to relate to the reader (e.g. personalisation – synthetic or otherwise – or features more typical of the spoken mode)
- How structure is used and created in the text – both at the discourse level (the shape of the text as a whole) and at the sentence level (written language can allow more manipulation of syntax)