Since I only wanted to have a little fun, not challenges, I only played Prince & Monarch levels before and just started on Emperor for two games just to check out how difficult it is.
My first Emperor game was a breeze, absolutely no sweat at all so I was a little taken aback since I expected it to be hard from all that I heard (I learned why the first game was easy when playing my second game). In both games I took whatever the map generator gave me. I just happened to have a great position in the first game, with a gold mine by a river and three food resources !! Not only the gold mine helped the early techs greatly, it also removed the crippling happiness cap at Emperor level, making my game almost Monarch-like.
Anyway, I used the same strategy I used in Monarch, but since the starting position was so blessed with resources, I decided to skip Bronze Working and went straight for Alphabet (via the Animal Husbandry route to take advantage of the Pig and Cow resources) before trading for all the lower techs, including Bronze Working. I used Qin SHi Huang in both games, BTW.
I was in the eastern side of the pangae, surrounded by Mali in the North, Mongol in the West, and India in the South. One big decision came when I got a Great Artist after Music. At that time, I got hemmed in on the West side by both Mali and Mongol since I expanded to the North (and choked Mali to a total of 3 cities before running out of land) and South. I had a hard time deciding where to use my culture bomb without triggering an immediate war. In the end, I used it right in my capitol instead of in a border city. It turned out to be a good decision since both the Malinese and the Mongolian cities on the West side flipped to me. Since Mali only had two cities left, it had little choices other than building up an army and attacked me. It took a while but I got his capital before granting him some peace.
The rest of the game was just routine cleanup. I founded Confucianism and Taonism (I got significant tech lead even by that time). and eventually wiped out the Mali, the Mongol (leaving one island city), and the Greek (what a huge army it had. Even my tanks and armoured Infantry had problem with his riflemen). At the end, I took just enough cities from India (who was pleased with me but always voted for Cyprus) to vote for my diplomatic win at the UN in the 19th centure. I still had one spare GP and three spare GEs at the end of the game without finding anything useful for them to do since I had already built all the late game wonders. It was no match and I could have built two SSs with my huge production before the AI coud even start on one.
My second game was a different story. I got stuck on a peninsula in a pangea map. It's mostly jungle, low on trees, the only copper resource was 4 square away from the Greek capitol, no gold, no silver, no marble, no stones. Militarilistic Rome and Greek blocked my exit from the penninsula.
I figured the only way I could survive would be to wrench the copper mine from under the nose of Greek so I did just that and tried to fill in the gap in between (barely). The maintenance cost brought my research rate down to 10% and I was toasted tech-wise in the early years (after finishing Writing, I switched to Alphabet and it was supposed to take 58 turns to research !!). The GS from the library helped a little but I was forced to trade away Alphabet shortly after getting it to close the tech gap somewhat (I made a rule never trade Alphabet away before). After getting the GL, things improved and I got to Liberalism first (with 100% research, using the gold obtained by trading my higher-cost techs for the cheaper techs plus gold). The AIs don't seem to care too much about gold, BTW, only on the tech research cost (and how rare/common it is) so it is a good strategy to sell the same tech to different civs which have money.
At this point, around 800AD, I think I'm a little ahead of the AIs in tech but there's no military force worth speaking of. I survived by giving the AI civs whatever they demanded, especially my neighbors Rome and Greek. Greek is pleased with me after I joined him (verbally anyway without sending any troops) in a war against India. Rome could be more treacherous but, hopefully if I give him what he wants then I can buy time to develop my infrastructure before building up the military for defence. I see if I can play a peaceful game and win with the SS this time. Still playing ...

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Biggest hurdle I found at Emperor level is the crippling happiness limit of 4 in the capitol and 3 in other cities. With a good starting location and good resources, it's not too bad otherwise with limited number of cities (due to maintenance cost) and limited number of citizens as well, it would be hard to compete with the AI's advantage. If all the happiness resources available require Calendar, as in my second game, it might be quite a task just to survive until getting Calendar without being completely out of the tech-trading loop and if you're out of the tech-trading loop then you might as well give up since you can never wipe out 6 remaining civs fast enough while being behind in tech no matter how big military build up you have.