In the past, I had made scientific posters using Adobe Photoshop software. The software was more complex than I needed. More recently, I have used Powerpoint to make posters. You really only need the following functionalities:
writing text and text headers
importing images and spreadsheets
drawing basic shapes and arrows
Creating a customized poster size To create the proper poster dimensions, go to the File menu and select Page Setup. Select Custom slide sizing, and enter the appropriate dimensions. In this case, I selected 50'' x 50''.
Be sure to follow the poster dimension criteria set by the conference that you are presenting at. I was once at a conference where the presenter couldn't hang her poster because it was too large.
Use a white background. A colored or gradient background can turn out unpredictably at the print shop. Remember that screen image quality does not always mirror print quality.
When you are all done with the poster, zoom in to 300% size to determine if the print resolution is adequate. Pay special attention to imported images.