Find an editorial Illustration you admire. Such as this amazing illustration by Mike Byers on the topic of Bed Bugs. 🙂 Read the subtext about the illustrations and where / how they were used. Analyse what metaphors they chose to illustrate the subject matter. Observe the way the artist has conceptualized their subject.
Pay attention to what methods they have used:
Here’s a few places to start looking:
But most of all, just look.