Too much information
The essence of an infographic is to distill a lot of data into a more readily digestible form. It might take a little bit of work to reduce a complex idea, or several ideas and statistics, but it's an absolute must or the infographic will end up looking chaotic and effectively becoming a disheveled representation of whatever the message was intended to be.
Before any design begins, edit the information just as you would edit any summary. Take out superfluous information and leave in the most impactful and useful information. Leave out redundant facts that might cause a loss of interest and don't try to shoehorn in a tidbit that doesn't offer any substance.
Data is equally weighted
There should always be a hierarchy within the information. The bottom line is that it's boring to simply be shown a picture and a percentage and then another picture with a percentage. Once the summary has been created, the next step should be to decide what the key messages are and which parts of the summary are supporting ideas. This organization ensures that the key points are heard and supported rather than expecting the viewer to decide what's important about the information. After all, the purpose of the infographic is to offer a simple interpretation of a collection of facts or ideas.