Hi
Im assuming all standard settings ?
I play almost all my games at deity, huge, marathon, pangea,
so any advice from me should be seen in that light.
The diplomacy game gets even more important on huge maps, since there are more civs to deal with.
I also set up my games according to the hall of fame rules.
This lets you change some of the advanced settings.
The most important setting, is the ability to handpick your opponents.
If you want to play domination, its very helpfull to choose civs who are very tolerant towards warmongering. Another important factor is friendship willingness.
Friends are less likely to go against you, and will let you sell resources at a better price. You need a strong economy, not only to support an army, but almost more important, in order to bribe other civs to fight eachother.
But even with those settings, you still need to be good at diplomacy.
First off, never take out city states.
Its ok to declare war on one or two, in order to steal some workers, and train your army. But never actually conquer one.
It gives a huge warmonger penalty.
On the other hand, be on the lookout for other civs taking city states.
If you can liberate a conquered city state, you will not only get an ally, you will get a big liberation bonus that reduces previous warmonger penaltys.
Secondly, try to make the other civs fight eachother.
Sometimes its very hard, and the price can be very high, but its something you have to do. Its best if it is civs close to each other, since then they will actually fight each other, but even if thats not the case, its still worth it, in order to make them hate each other.
If any cities changes ownership, it will also be a great target for liberation bonuses later in the game.
The warmonger penalty for capturing a city is lower, if your enemy has many cities.
So the best way to take out a civ, is to just conquer their capital, and leave any other cities alone. Sometimes you also need other cities, if they have very good resources, wonders, ore a blocking your way, but then try to get those cities in a peace treaty.
Cities taken in a peace treaty deal (or any other deal) gives no warmonger penalty.
(unless you raze them)
Try not to go to war alone. When you are ready to attack someone, ask/pay others to
join in. This will halve the warmonger penalty with your ally/allies.
(but make sure you are not the victim of a killsteal)
Keep your promises.
Dont expand where you promised not to.
Dont mobilize near a border, if you are not ready to declare war yet.
Dont denounce or attack anyone you have a friendship agreement with.
So dont make friends with someone you will attack soon.