Tried an experiment in my second game: I thought perhaps it would be beneficial to advance as far as I could as quickly as I could along one particular line, rather than spreading out the techs.
Turns out that's a bad idea. For a time I was ahead of everyone, but I soon realized my cities couldn't actually build much in the way of improvements. Which left me not much to do except pump out workers and Swordsmen. Well, the Chinese were right next door, and I'd already bottlenecked them from spreading onto much of my continent, so I thought maybe we could fight a bit.
Well....harder than it seems, pre-catapult, and that's along an entirely different tech line. My efforts to catch up on the tech front were very slow-going.....by 100AD, I was ranked last in technology.
So yeah, don't do that. (Noble difficulty BTW.)