Science is based on experiments and experiments give us data. The correct visualization and presentation of that data is key in scientific presentations. To get started in the topic I present some references on the visualization of data.
Visualizing data looks easy, but it isn't. There are different kind of techniques and tools to produce data visualization, not to mention the different type of data. Even creating a clear and accurate time series requires knowing what we are doing. We need guidance.
So, where to start? Two great books are The Visual Display of Quantitative Information from Edward Tufte and Show Me the Numbers from Stephen Few. I encourage you to look at their homepages. Another two interesting blogs are David McCandless' Information is beautiful and Andrew Vande Moere's Information Aesthetics.
Now, charts, graphs and tables don't say much by themselves. Data needs context, and that's why you there for. Don't let people alone get their own conclusions about your data, help them. What are the implications of the displayed data? What is the knowledge behind that data? What is important? What's not?