Before you start your project have a good look at other panels. See our gallery or do an internet image search for examples. Note what you like or don't like about individual designs, which ones are you drawn to and why? Notice how much of the panel you read, and then how much you remember. The key to a good panel is to keep it simple.
Think about who are trying to connect with. If it is the general public you will need to keep the messages simple and assume a minimum level of prior knowledge.
If you think some of your audience may already be fairly well informed, then consider layering your information with more available through online links or leaflets.
If writing for children think about including quiz questions or a fun character to get their attention. Can you want to include a more formal section for adults?
Exactly what message do you want to share? Write down the bullet points that need to be included and mark up which ones are the most important and which are the most interesting.