The Data visualization: A view of every Points of View Column in Nature Methods provides a fairly comprehensive overview of best practices. Here are a few highlights
- Check for journal guidelines or requirements
- Sketch out your ideas (you don't have to be good at art)
- Focus on key message and use the simplest visual representation
- Objects that interact or share common meaning should be formatted in a similar way
- Choose colors to avoid bias and are accessible to those with color vision deficiencies
Here are some other (shorter) best practices lists: