There is a lot of great advice out there on posters. Check the key post section of: http://betterposters.blogspot.co.uk Far too much text for a poster is the main mistake we all do: https://dynamicecology.wordpress.com/2016/03/22/the-one-big-mistake-almost-every-scientific-poster-makes/
My own pet peaves:
- Don’t use images unless they have a function/caption/in text reference
- Use conceptual figures if you don’t have data (eg. diagram showing link between hypotheses). Another type of conceptual figure is to present what you expect your results to look like (the plot can just be drawn in power point).
- Have a few key references in short form (Author year title journal)
- Far too many colours! And thanks to PowerPoint, it appears that the 1980’s will always be well alive in the colour schemes of scientific posters.