I'm the kind of person who HAS to watch things in order. That's just me.
So I would personally start at season 1, episode 1, (Rose), and go from there. The first episode is very wonky. But you'll later learn to love it.
It's a hard show to sell from my end, because I've seen it from the first episode on, and the first episode, I did the same thing.
... THE **** DID I JUST WATCH??
But it gets SO much better. By the episode entitled "Dalek", you should be hooked. Then the Moffat episodes start "The Empty Child" and "The Doctor Dances" with my favorite character, Captain Jack Harkness.
If you wanna jump around, I'll let you know about other episodes.
But if you start from the... Start? At the end of season 4, there's few 'specials' you need to watch before season 5.