Some pages in a site I drive AdWords to are getting indexed and are moving up. While I appreciate getting free clicks and conversions, this can only screw up the stats I use to determine how to tweak my AdWords. Do you let your PPC pages get indexed or not?
In some cases, yes. Most analytics packages make it very easy to determine the traffic source - paid vs organic in this case.
I would agree with GuyFromChicago. Most decent stats packages will allow you to differentiate. If you don't have a stats package, you can use Google Analytics for free.
I leave them indexed too. Just turn on automatic click tracking in AdWords, which adds the ?gclickid stuff to the landing URL. Analytics can then easily see who came from where.
As we tend to run both PPC and SEO campaigns for our clients, we tend to run PPC campaigns on campaigns until they get to the top of the natural results. After that, we discuss with the client whether to stop the PPC. Since the natural traffic is free, stopping it to make PPC easier seems a bit strange to me - you can manage a PPC campaign (to an extent at least) using just the Adwords data...