ask dr. lazyweb: running

The contingent of runners on my friendslist continues to swell.  I have always been antsy about the idea of running (shin splints! fallen arches! side stitches!) but I want to do more cross-training, and running is one of the most convenient options for me.  Therefore, in lieu of doing actual research, I ask you!

What are the most important tips you all would want me to know?  What do you wish you knew before you started?  I know I need decent running shoes, so I'll be making a trip to Marathon Sports, maybe later this week -- but what else?  Running on pavement vs. dirt?  Different kinds of pavement?  Are there secret posture tips I really need to know?  etc. etc. etc.  Is there some web site that will tell me everything the world knows on the subject (like sheldonbrown.com for biking or stumptuous.com for lifting)?

Talk to me!