1. The Eleventh Hour
This is the introduction of the current Doctor (for a few more months, anyway), and it's a perfect way to jumpstart their foray into modern Doctor Who. If they're not the type to go for the old black and white episodes or Pertwee messing about in a cape, you might be well-served to go straight for Smith. It'll be easier for them to catch up to the present, and if they're hooked they can go back and watch Eccleston and Tennant. As far as regeneration episodes go, this one is a gem. Smith is immediately winning as the new Doctor, who's a bit wacky and odd, but in a comforting, familiar way. Sure, the whole Prisoner Zero plotline tends to feel like filler, but that's not the point of the episode. Smith has about an hour to make us believe once and for all that he is the Doctor, and with the caustic yet somehow sympathetic Amy Pond by his side, he does that and more.