1. Succinct and Descriptive Graph Title
2. Sort Your Data BEFORE Charting
3. Spacing Between Bars
4. Clean Up the Axes
Vertical or slanted text on a poster forces viewers to tilt their heads in a usually uncomfortable manner in order to read your graph. An easy way to avoid this is to switch axes like the example below.
5. Modify Grid lines and Background Color
Microsoft Publisher allows you to modify all of these aspects of your graph. First the background default is usually set to showing grid lines behind the bars. In most cases you would want to remove these.