Strategies change when you're talking Emperor level and higher.  Mistakes that would have set you back a little in lower difficulty settings could cause you to lose in Emperor difficulty level games or higher.  What strategies do you guys use?

Please share, even if you think its trivial.

These are not necessarily "the best" strategies and I know there are others, but here are mine.

1)  Great Wall.  In lower difficulty settings, I tend to build up my capital with a wonder or two before expanding.  Maybe founding a religion at times.  On Emperor... nuh uh.  Prioritize your wonders if you're going to chase them at all, because while you're spending far more production units than the AI would on a wonder, its building cities, military, etc, so it had better be worth it.  In lower difficulty settings, I value the Great Wall near what I would on the other wonders, but to me on Emperor level, I chase it quickly and with high importance.

A warrior is fine to defend my capital initially, but then I build my Great Wall, a decent military unit (not a warrior!) and use that to protect my settlers as I SPAM out several settlers from my capital back to back to back.  Basically spam out until I have no more room to expand, using this same archer/horseman/axeman to defend those settlers.  Once the city is set, its 'safe' as barbarians cannot enter its border and that unit can then go defend another settler.  I have new cities build a worker unless my capital can CRANK them out rapidly afterwards.  If you're not developing your tiles with a worker, then that city isn't very useful. Then, start thinking military... barracks, wall, etc in these new cities.  Nothing else is as important at this time as I now have several cites poorly defended.  Build defense quickly, but you have a little time to spare before the AI eyeballs your cities.  The capital should be cranking out defense to those cities as well.  Warriors are okay in the middle of my empire, but I never, ever build warriors if they are to be used on my border cities.  3 or 4 defensive units on my border at a bare minimum.

2)  Capital city love.  All Great Generals go to my capital city, no matter what and even if the city next to it might eventually have more production.  High priority is placed on developing the capital's squares and dropping hamlets on the grasslands and especially on grass with rivers, or floodplains.  Develop it fully and quickly.  I go lopsided on my techs to get Civil Service early and switch to Bureaucracy asap, which gives you +50% Hammers, +50% Gold in your capital.  I might ride an entire game out with this civic if its on Emperor difficulty.  This is why you build hamlets asap and why you send all generals to your capital.  I plan on building the Heroic Epic National Wonder in my capital city every single game.  For the 2nd National Wonder, maybe Wall Street (+100% gold) or Oxford University (+100% science), but if your capital is on the coast, then the Moai Statues would probably always be my 2nd wonder as you want your capital city to be your juggernaut city.

With +50% production, you can keep up on new buildings as they become available (libraries, banks, etc) and crank out military units when they're not.  Civil service with the Great Generals in your capital can make your game once you have the Heroic Epic.  Cranking out experienced units left and right is a beautiful thing.  +50% gold in your capital can allow you to turn up your science slider a couple notches (Several more if you have a religious building in your capital making gold).

3)  Tech priorities.  I always go lopsided a bit to get Monarchy early for the happiness that Hereditary Rule brings to your land, and of course, to my capital city.  I wouldn't build the pyramids to get this, as thats waaay too many hammers to build on Emperor difficulty.  If I have stone, then thats a different matter and I might go for it then, but otherwise, go get Hereditary Rule with Monarchy.  2nd, go a little lopsided to get Feudalism as longbowmen will keep you from losing cities for 1/2 the game.  I will often try to build the Oracle and time it so it gives me Feudalism for free.  Stick 10 longbowmen in a city being invaded and you likely won't lose many, if any of them.  Some games (see my Civ Brazil one a couple months ago) I've had stout longbowmen fending off musketmen and grenadier invaders.  With at least 2 city garrison promotions (+20% and +25% defense) along with its base +25% city defense and 1 base first strike, forified long enough to have +25% defense.... it is the single most important unit in the game, in my opinion, as it will defend you for at least 1/2 the game, and will during the important 1/2 as you set yourself up to win the game during this half.  This tech is very important to get early and to defend your border cities.  Couple this with your capital cranking them out with Heroic Epic and Civil Service.  Oh yeah... Civil Service.  lol.  Go a little lopsided to get that shortly after Feudalism so you can switch to Bureaucracy asap.  As the game goes on, I go lopsided to get Military Tradition/rifles as cavalry rules for quite a while.  Basically go lopsided for the units that will rule its age.

4)  War.  If you have equal land size as your neighbors, or even close to it, they will dwarf you in tech on Emperor difficulty as time goes on, so you MUST go take cities.  It is hard to get a lot more units than your neighbor on this difficulty, so you have to be smarter about warfare.

If I'm going to have build up offensive units, I will switch my civics to Theocracy and maybe Vassalage to crank out experienced units.  I do this en masse and have all, or nearly all my cities switch to making military units while the civics have changed.  Once I'm done building up (maybe after a war?) I switch back.  If my other cities suck, maybe I'll just switch to Theocracy and keep my capital's +50% bonus on Bureaucracy.

Again, its worth saying twice.... if you linger on warfare on Emperor level games, you will lose as you cannot compete in techs (if you're near the same size as your neighbors).

Thats all for now, as I'm creating a wall of text.

I like Organized Religion while building up as its like a factory with its +25% production.  All my cities (or nearly) build buildings together with that bonus, and then all (or nearly) build military when its time to pick a fight, or defend after a sneak attack with Theocracy and maybe Vassalage civics.  Then, back to Organized Religion.

See Catapult/Trebuchet/Cannon stragegy here.  Critical to bring siege units and several of them when attacking.  If you use them properly, you should never lose an offensive attacking unit, other than a siege weapon or two.  If you lose a trebuchet to take a city, then its a great swap.  With some Great Generals, your capital could be making some very nice trebuchets with all city attack promotions.

Scouts as medics.  With Theocracy at a minimum, you can make a scout with 2 promotions, which I build each and every game as a medic.  I will stick one in a city being attacked and 1 in my stack of offensive units.  If your attack force gets catapulted while outside of an enemy city, its no big deal with a medic in your stack, where you might have to retreat otherwise.  Scouts maybe take a turn to produce, can move 2 spaces and won't accidentally defend against an attacker and die.

Don't automatically attack with the best units.  Lets say you have 2 swordsmen that are very stout with 3 city raider promotions (+20%, +25%, +30% attacking cities) on each of those 2.  Lets say you have 2 average swordsmen with maybe 1 city raider promotion on each.  A city is defended with 2 longbowmen.  Your 2 stout swordsmen will probably lose while attacking, and then your average ones following up the attack will possibly lose as well.  Do it in reverse order, sacrifce the 2 average swordsmen by attacking and you may win that battle with your 2 stout swordmen attacking weaker units and make them even more stout.  Make sense?  Your stout guys may have a 50% chance of winning outright initially, but once you sacrifice 2 average guys, you might have a 90-95% chance of winning.  If you lose your 2 stout units, your weak ones may have a lesser chance of success and even if you win, they won't be nearly as stout as if you did it the other way around.  Pay attention to the % chance of victory and don't just throw away magnificant units.  I do this with trebuchets as well.  A trebuchet with 3 city raider promotions may have a 30% chance of victory on the 1st shot, so waste your worst trebuchet on the 1st attack and then your experienced ones may walk over the remaining defenders.

If tech trading is on, don't fall behind on Emperor even if you have to trade some techs you'd rather not.  Once you're beating neighbors down and getting huge, this may not be as important.

Oh and hamlets are totally underestimated by some.  This is not just money, but science and it rises as the game goes on, so build them early.  Don't be afraid to have a city governor emphasize commerce, or do it in all cities at times to quickly get a tech (money = science).

Enough for now.  Would anyone else care to share theirs?

wtf didn't I think of that before? Everything else I kinda knew. I spread my GG's about a bit more - mostly in the cap but the rest in the major ship production city (it all depends on the map, doesn't it?) I try to get two military production centres going because you can share the limited National Wonders between them more evenly.

Medic Scouts.  Love them.  Explorer medics... not as much because they cost more, but also because if your stack gets pummelled enough, they *could* actually defend sometimes and of course die.  Then your remaining stack could be in trouble.

If an AI is throwing wave after wave at 1 city, any medic can help it heal up quickly, but going with offensive stacks is priceless, IMHO.  I think in general, medics are overlooked by many players.

Probably true, but who knows? I generally give healing to the obvious guys like pikemen and machinegunners and the occasional superhero general (and always privateers) but scouts - that's a great idea!

Another question: how much of your gold do you spend on research?  This starts with 100% but keeps dropping as the game progresses.  If you fall behind in tech, how can you win either in space or militarily?