Read Strunk and White's The Elements of Style.
Formatting:Patrick Baudisch set up a web page on posters for UIST, it is relevant for any other conference. He wisely suggests to let Google give you some more tips.
Collin Purrington has a nice article on designing conference posters. He also manages the Poster Sessions and Pimp my poster Flickr groups.
This is an endless topic, but here are some universal tips that would work for any non designer: lessons from swiss style graphic design by Smashing Magazine.
Check this curated list of great infographics, look and get inspired!
The aim of a poster is to convey information clearly in a printed format. The best way to get there is to use software that lets you organize information and print it nicely. So using a software made for detailed page layout, text flowing around images and handling of high-res pictures is best.
I tend to favor those over over lab exp.
Scott MacKenzie set up some useful pages:
LittleStat(alpha) is a great tool to calculate statistics online. It also helps to pick the right statistical tool for your analysis through a simple series of yes/no answers.