Here a few important questions to ask yourself when creating something visual (presentations, newsletters, flyers):
1) Why will my audience care?
2) What do I want my audience to remember?
3) How do I want to design it to be visually impactful?
4) How can I simplify my message to fit the design yet still be meaningful?
The more time you spend answering these questions during the early stages, the better your final product will be.