Are you a complete pleb? Do you have absolutely no idea how to become a true Whovian? Did you watch the first few episodes of Nine and think "god what the fuck is this shite?" (Of course you didn't because Nine is awesome) Well, you are not alone! With this comprehensive guide, you should be able to into Doctor Who faster than McGann can whip up another audio play from the Based-ment.
Method 1: Don't Edit
After that, you'll want to look up what most people consider to be the best episodes of each Doctor and start there. The list of comfy episodes does a good job of hitting all the good (and bad) that Doctor Who has to offer. There's also the GOAT guide and the Golden Age guide. Be sure to familiarise yourself with The Best Doctor too.
Method 2: Find a favorite Doctor and watch everything in his run, then pick another favorite, etc. Edit
Pretty damn self explanatory. If a certain Doctor piques your interest, it may be a good idea to see what that Doctor's TV tenure has to offer. If you're very devoted, you could also get into the Big Finish audio plays.
Method 3: JUST WATCH IT ALL FROM THE BEGINNING YOU PLEB Edit
The only correct method. That includes the spin-offs. And movies. Then read all the books. But don't forget the comics. Then listen to all the audios. Now report back to /who/ for further instructions.