These are a couple of useful articles on how to create a good poster:
Communication Skills for Biosciences by 
Research Project Success by 
Study and Communication Skills for the Biosciences by Here is a suggestion for a generic layout of a poster. This one uses the University poster templates which are available to download from Design and Print
They also have guidance on style and how to format and layout the text on the poster
Top Tips!
Don't illustrate your poster with pictures unnecessarily - images / figures should be relevant
Font size should be legible at a short distance - remember your final poster size!
Make sure it's clearly organised - use section headings or numbers to make reading easy
Avoid extensive writing - be concise!
Make it an appealing colour but don't overdo it!
If you would like to use the University style for posters, Design and Print have some templates for University branded conference posters and guidelines on how to format your poster.
The Study Advice team have put together a great guide on preparing and presenting your poster - including tips on layout.