There are many different ways groups do this on flickr, but the one group I seem to like the best is http://www.flickr.com/groups/project365/ and their rules are right on the front page. I will be following those to get started. If anybody wants to try this with me let me know so I can keep track of your days. Over at http://www.flickr.com/groups/project_365 they have tons of others who participate in this every day, and I also noticed they post themes every once and a while for you to try out if you run out of ideas.
Just a fun picture I took a while back to share with you: