I am currently running PD M520s on my summer bike and they are a good starter set in my opinion.
As far as what the other posters have said regarding what design concept to get, I have to agree with them that if you get pedals, do not get the ones that have clip-ins on one side and a platform on the other. Get the ones where the clip-ins are accessible on both sides of the pedal if you do decide to go that route. When you get them put on, practice, practice, practice. Find a nice soft patch of grass, clip in, clip out, both sides, try and go as slow as you can before you clip out, then go slower. Go so slow that you are almost falling over, then do it again. It may seem stupid, or monotonous, but when you are on the trail and you really need to clip out, it'll pay off.
Also, pay close attention to the instructions about putting the cleats on the shoes. They'll save you having to get new plates when you have to have them drilled when the screws bind.
Have fun!
