What are some general good principles for creating a poster for a poster session? Should one create slides similar to those that one uses in a good powerpoint presentation? Or are there things that a poster should include that a powerpoint should not include? (and vice versa)
The title is your bait, the first paragraph is your hook. Make the bait big and tasty, make the first paragraph catchy.
A poster is primarily an advert for you. Secondarily, it's an advert for your research. Thirdly, it's an advert for your department. And it will succeed at those things best, if it gives the casual reader an easily accessible introduction into what's novel about your research.
Know the flow: it should be clear to anyone reading, what they should read first, then second, and so on.
Make it clear that it's your work. Get your name and affiliation in big letters, with a photo of you. Include your contact details, and make sure you can be reached on them during the conference.
Don't use powerpoint. A poster is graphic design, so use a graphic design package such as InDesign. If you don't have an eye for graphic design, design the poster with someone who does. Most departments have at least one natural talent. It's often the person who keeps winning the "best poster at conference" prize. It's orthogonal to (i.e. independent of) quality of research.
Use a big, clear typeface. Not everyone you need to reach has the healthy, clear vision that most students have.
Briefly state the problem, the method, the results, and the implications.
Pretty pictures are crucial. The words are there just to supplement the explanation of your work given in the pictures.
Test, test, test. Print it out life-size (tiled sheets &amp; sticky tape are your friend), show it to a couple of colleagues (one hot on your area of research, and one hot on design), watch the order in which they read things, ask for feedback. Implement any advice on content that comes from the one who is hot in your area of work. Implement any advice on design that comes from the one hot on design.