Writing a graphic novel is a team effort - author and illustrator. I'm really lucky to work with Peter Richardson on the Boffin Boy books.
When you're the writer of a graphic novel, you only have speech bubbles and captions, and sometimes this isn't enough to explain what is going on. It's really difficult to explain how the various characters are feeling. In a story written the usual way, you can add useful adverbs - 'she said angrily/sadly/inquisitively' and you can describe what the characters are thinking. 'She listened to his story, but she didn't believe him'. This just doesn't work with speech bubbles.
That's where the illustrator comes in. Peter is really good at drawing faces. When you look at someone's face you can get a pretty good idea of how they are feeling. Have a go at drawing faces to match feelings like surprised, or grumpy, or frightened, or trying not to laugh but you just can't help it.
It's not just faces. Hands are important too. Think about all those different ways we use our hands too take the place of words. How do we hold our hands if we haven't a clue what is going on? (That happens a lot in Boffin Boy books!)
There is one little problem. Boffin Boy books have been translated into different languages and are read in lots of different countries. Different people use their hands in different ways to show what they feel - and sometimes what is friendly in one country can have a very different meaning somewhere else - and could even be quite rude!
So - if you like the idea of writing and illustrating graphic novels - my advice is to practice drawing hands and faces!