for me i love all the Civ's & i been playing for such a long time, i look at current world politics & see how i can improve upon the real world as if it was a civ game.
For me i love either playing the japanese, or germans above all others.
For all games i play i keep restarting the game untill i have a good restarting location(searching for the 1st turn to 4th turn maynot seem that important, but it is veyr important, you dont want to give enemies a heads start on you.
Once i got that started, i work towards making 4 to 7 cities while not hampering my capitals growth. i like to ring cities(closest i would place near capital is a min of 10 tiles away around my capital to allow for growth)& have roads(then eventually rail) linking all of them. i would keep some attacking units in def mode 3 to 5 tiles away from capital, with one open space in between each unit in def mode.for other cities i would keep units in def mode 2 or 3 tiles away facing away from capital.
If capital is on coast line, then i tech up to gallons & eventually steam ships. i always kept 2 or 3 attack ships patrolling the coast line near my capital. on land i do as much of a ring of cities as i can.
with other civilizations, i would make peace with anyone i come across(& maintain that peace as long as i can) & if i can make them my allies. if anyone dont make peace with me, i try to goad my allies into attacking other civilization while not trading with them & refusing said units into their land areas. I would have allies & civ's i was at peace with weaken themselves before i am required to act on enemies.
with the germans their specality is the panzer tanks. so when i play them i would keep my science rating 10% to 20% beyond the 1st 20 turns.
overall i tech up as much as possible(keeping science at a min of 10% & at time as high as 50%) & i put all wonders in my capital(with forbidden city i place that on other side of map in areas i control). my capital being heavyly defended having a min of 5 of my most tech advanced units in city for defence. & having another 10 to 20 with in 4 to 8 tiles away from capital to intercept enemies.
Once i have planes i keep 3 to 5 planes/bombers based in capital, while i have 2 to 5 planes/bombers based in my ring of cities around capital.
With roads/rails leading into other civilizations i keep 1 or 2 units in def mode at my borders on all roads/rails. By time i get panzer tanks, at most other civilizations have knights or riflemen.
untill i get panzer tanks, i play heavyly on the defense & making peace with everyone i can(& maintaining the various peace's as long as i can) & playing my allies against my enemies to weaken my enemies
At this point i will only keep my capital producing tech or wonders, all other cities(upto 15 at most here) will mas s produce panzer tanks or most advanved attacking units, which ever is quickest to get. once i have a min of 20 tanks( i like to have 40+ depending on how many enemies i have) i will place them near my enemies boarders & place them in def mode to allow for my slower units to catch up(which can be upto 30 units). by time all slower units are on enemies boarder, another 10 tanks have been produced.
At this point in time my allies would have been at war with my enemies while those who i am at peace with refusing to trade with my enemies for 10 to 20 turns.
Now i reintroduce slavery no matter how my citizens see it or how unhappy they get. if any rioting happens i wait for it to stop.
Now i do a blitskerg with my tanks( 30 tanks at this point minimum & 30 slower units minimum to act as backup to tanks), i focus on 2 cities at most attacking them & i take them over & move my slower units in to garrison them( a min of 4 per enemy city for a min of 10 turns). as i slowly mov e into enemy terrority i leave my rear guarded by 1 slower unit eveyr 3 to 7 tiles apart & having 1 tank every 5 to 10 tiles apart. Now i bring in 20+ workers to build rail lines in recently aquired enemy cities & upto this point the workers were building roads/rails in allied civilizations or ones i was at peace with with open borders. Now untill that 1st & 2nd city had roads/rails connecting them to my main civilization area of map, i would hold back 10 tanks from my attack to act as defence from enemy sending units to retake city(s) i conquered & to act as additional defence for my workers. from here i would mass attack all cities as quickly as i can with the single road/rail line open to allow units to move from main cities into enemy areas.
once enemy is completely conquered, i would start sacrificeing citizens of conquered citys to rebuild them as quickly as i can.
At this point i like placing 3 to 5 tanks outside of all allied cities & all cities of everyone i am at peace at with. once this is done, i suddenly attack ALL cities.
within 10 to 30 turns, i literally conquered the world & latest it was ever was 1400 CE