How far, Doctor? Back, back to your beginning...

Back in October, a friend asked my opinion on the best place for someone who hadn't watched Doctor Who before to start. I answered "Rose," the first episode of the 2005 revival of the series. Googling "where to start" and "Doctor Who" suggests that I'm hardly alone in making that recommendation. I'm not sure I'm pleased with the prevalence of potshots taken at the perceived quality of the older seasons of Who, though.

While the vast majority of Doctor Who stories can be enjoyed (or, at least, understood) without any previous exposure to the series—thus, cherry-picking a few of the best episodes is the most obvious way to generate an interest to see more in the uninitiated—the level of connection that a Doctor Who fan achieves with the series can only occur when there is some appreciation of the show's continuity. Watching episodes in order is important, but there are some very good reasons not to start at the very beginning. I've identified seven particularly good possible starting points below and made a few notes that might help the new to Who work out how far back they'd like to go. Obviously, the further back one goes, the more primitive the production methods utilized become. Apart from that, here are some of the other points to consider.

• The Eleventh Hour - Series Five (2010)
  • The place to start if your goal is to get up to speed as quickly as possible.
  • You must go back at least this far. It's only 28 episodes.
• Rose - Series One (2005)
  • The best place for the new to Who to start.
  • Doctor Who's last regular season had aired sixteen years earlier. It was assumed most viewers would be unfamiliar with the show.
  • There are five episodes between Series Four and Series Five, collected on The Specials box set.
  • There are two spin-offs, Torchwood and The Sarah Jane Adventures, to keep track of (or ignore) as well:
    • Torchwood Series One slots in after Doctor Who Series Two.
    • Sarah Jane Series One comes after Who Series Three.
    • Torchwood Series Two is between Sarah Jane Series One and Who Series Four.
    • Sarah Jane Series Two aired between Who Series Four and "The Next Doctor."
    • Torchwood Series Three aired between "Planet of the Dead" and "The Waters of Mars."
    • Sarah Jane Series Three began after Torchwood Series Three and finished shortly after "Waters of Mars."
    • Sarah Jane Series Four aired after Who Series Five
    • Torchwood Series Four aired concurrently with Who Series Six.
    • Sarah Jane Series Five aired after Who Series Six.
  • Actually, there's a third spin-off: K-9, but its relationship with its parent program is not as tight.
• The Leisure Hive - Season Eighteen (1980 - 1981)
  • Classic series episodes are not released as season box sets, making it more difficult to obtain stories in order.
  • Some episodes have yet to be released to DVD at all!
  • The spin-off K-9 and Company aired between Seasons Eighteen and Nineteen.
• The Time Warrior - Season Eleven (1973 - 1974)
  • The first season to feature Elisabeth Sladen as Sarah Jane Smith.
• Spearhead from Space - Season Seven (1970)
  • Though originally shot in color, a number of episodes now exist only in black and white.
• The Dominators - Season Six (1968 - 1969)
  • The first six seasons of Doctor Who were shot in black & white.
  • Seven episodes are missing from Season Six (out of forty-four).
    • The BBC destroyed the master tapes of many programs they thought were no longer of interest in the 1970s.
    • The audio of the missing episodes was preserved in recordings made by fans.
    • Animated versions of two of the missing episodes are available (completing the serial "The Invasion").
    • The other five missing episodes are all from "The Space Pirates." Just skip it, or get the audio or a reconstruction.
    • This is the earliest place you can start without being seriously inconvenienced by missing episodes.
• An Unearthly Child - Season One (1963 - 1964)
  • 106 total episodes are missing from Who's first six seasons (out of 253).
    • Audio versions are available, as well as fan-produced reconstructions.
    • While seasons one and two are relatively intact, seasons three through five barely exist in their original form.

From Wikipedia (you'll want to keep this handy): the List of Doctor Who serials.