Major points to keep in mind for presenting your GIS data on posters, etc
make the poster flows from one element (the idea, the data) to the next (the methods, the results) by using organization, or arrows, or colors linked to a model
emphasize the methods, geographic data and results by limiting the amount of writing and making these necessary parts the largest part of the poster
support the geographic data with plots showing differences as needed (or if absolutely necessary and small, tables). Graphs should have a small caption and the axes should be labelled.
if you use your geoprocessing model on the poster (usually not a great idea), simplify it by editing it into section that show the process used in the GIS. Considering drawing a simplified model if you want to use one.
simpler is usually better (less is more). Use only what you need to get your viewer to see what you did and discovered.
Remember to compose your scale bar and legend with logical units and clear divisions
use continuous color ramps for ordinal/rational numbers, and random or selected colors for categorical data (unless, like an index, they have order)
be careful of overlapping maps, they may not print well. If you plan to put other material on top of the map, send map dataframes “to the back” by right clicking on them
Could your audience be colorblind? Here’s a fun website for creating maps that differently-abled people can see. https://colorbrewer2.org/