That's the spirit
Just some small tips in addition to AlanH's url. Most of you know theese tips, but I hope some of it can be of use.
- Tunneling. Scout as deep and straight as possible as early as possible with your first warriors, don't wander to far from a straight line on the map. Once you hit a coast you can take the luxury to wander around. The speed of opposition expansion can close a potential door to further contacts. Don't put your first warriors to garrison your towns. Send them out.
- Excersize the slider. Don't be afraid to do a very early scout with warriors. Many players prefer a 0% luxury game, but on higher difficulties you must slice every ounce of opportunity to use the luxury slider. Trim it up and down as your town grows and shrinks. Scouting the terrain for luxury, huts(restless barbs make huts more attractive) and contacts is more important than getting a tech or a few pieces of gold a round faster.
- Share garrisons. Roads = fast and moveable garrisons between your early cities. Spot the time when a town grows, and be ready to send a garrison there. Roads before mines/irrigation let your workers do a fast retreat and also bringing your national guard quickly to the workers when the more potent vanilla/PTW barbs appear. A warrior at a content city is a waste of good military police powers.
- Archers are important while fighting barbs. Later horsemen. The time when you could safely send a warrior against a barbarian HM or warrior is past when you play at emperor level. I usually have an early archer for aggresive hunting of barbarians approaching my borders.
- Luxury. Don't hesitate to send a settler to far regions to claim luxury as early as possible. It might seem safe to wait, but the AI's expansion speed is noteworthy faster at Emperor. If it's close to their capitol you might want to slap a temple in there fairly soon to counter the chances of any flips caused by your rotten emperor lvl culture (workers, warriors and settlers don't generate much culture
- Trade, trade and more trade. Check that foreign advisor for any trade every round. It might seem tedious, but missing a techtrade window, or worker trade is so much more impairing at higher difficulties.
- Firm science. Don't go halfway with your research. Either go at max rate, or opt to trade it for gold at minimum rate. Allways find the minimum level of science slider when you have one round left on research. You can save a lot of gold this way.
- Excersize your citizens. Count your food and shields and find out optimal distribution of your citizens on the valuable worked tiles. Your first cities must share worked tiles since you will most likely grow faster than your workers can improve the terrain. Though you should also have a higher worker count. I try to at least have 1 - 1.5 worker pr city, though this is very hard to do while expanding fast enough.
Every round will go much slower on Emperor level because of the level of micromanagement and time spent checking foreign advisor. Don't play too long and risk doing mistakes. Save the game often and get some fresh air to counter the boredom/tiredness. Good luck!
PS: Can't mention often enough the value of studying good players timelines in the higher difficulty QSC's. You find the URL's at the main GOTM site at the bottom left side of the screen under each GOTM.
Or not. 
Many thanks. I especially like the one about tunneling. 
