Don't pack in too many words. Depending on size of poster; no more than 800 words for large poster, about 400-500 for medium size
Minimize text - use images and graphs instead
Use phrases rather than full sentences
Avoid blocks of text, use bulleted lists of sentences instead
Use an active voice
The title should take up only 1 or 2 lines
Title in sentence case – lower case letters easier/faster to read than uppercase. No italics, title case, or all caps
Your title should be interesting, easy to understand, and encourage the reader to check out your poster in more detail
Use a non-serif font for title and headings and a serif font for body text. Serif-style fonts are much easier to read at smaller font sizes…
For the title, consider using a large, bold san-serif font, such as Arial Black, Franklin Gothic Heavy, Tahoma, Trebuchet, or Verdana.
For the subtitles (authors' names, school name, etc.), use the same font as your title but make the font size smaller than the title.
For the section headers(Introduction, Results, etc.), use the same font as your title and subtitle. Make the font size approximately 50% larger than the body text. Make sure that all section headers are the same font size.
For the body text, choose a serif type that is very readable, like Garamond, Book Antigua or Bookman Old Style. Make sure that the body text is the same font throughout the entire posters.
Be conservative. This is important for two reasons. First of all, familiar fonts are easier for your audience to read. Secondly, your poster will be printed from a different computer besides your own. If you use a font that is not installed on that computer, a different font will be substituted instead. (If it is absolutely critical that an uncommon font be used on your poster, you can save it as a PDF or contact your printer to see if they can install your font.)
Don't underline text; italicize instead
Left-justify text; avoid centering and right-justifying text
Background and Colors
Use a light color background and dark color letters for contrast.
Avoid dark backgrounds with light letters - very tiring to read.
Stick to a theme of 2 or 3 colors - much more will overload and confuse viewers
Don’t use colors that will make posters hard to see for viewers with color-vision deficiency e.g. black & red; green & orange
Charts and Graphs
Graphs should be simple and clean
Use simple 2-dimensional line graphs, bar charts, pie charts
Avoid 3-dimensional graphs unless you're displaying 3-dimensional data - and then proceed carefully, as many 3-D graphs are difficult to interpret.
Place titles or informative phrases on charts and graphs
Write explanations directly on figures instead of referencing from elsewhere
Don't use complicated legends that require the reader to constantly look back and forth between figure and legend
Minimize abbreviations and cross-references
If you’re looking for a good generic photograph of something, try searching through Flickr Creative Commons, or in Google Images, look for Tools>Usage Rights; using proper credit of course
Give the source for any image that is not yours. Only use images (illustration, photograph, etc.) that are fully public domain. If it’s not public domain then you are probably violating somebody’s copyright.
Images & graphic resolution = 150-300 dpi so the image doesn't look fuzzy