I have never won a diplo, cultural or science victory. All I have ever done is domination. I play on level 7 diff these days. I don't know if it can be done as easily with this new patch since poor warmongers like myself are penalized by no longer having a courthouse give + 6

insteand it's only +3
The keys to happiness and you'll never really have much. You'll always be sweating it until the end. Your cities will never get about size 18 or so either.
Build your first 3-4 cities spread out bodly going for luxury resources and then iron. You are basically saying, "This is where my borders will be."
The exact strategy is
here.
Go liberty for your first policy tree and the only one you'll finish. You may be tempted to do honor as a warmonger, but don't. The -10%

, +1

per trade route and free great person are too big to pass up.
Try to time your technology after beelining iron working to get theology and then education. The cool thing is that you should finish Liberty right around the same time.
First, build Hagia Sophia. +25% GP generation and another free great person which you will use to select a new engineer for
Notre Dame +10

This will get your first big expansion in

. Either wait for your cities to grow up or use it to take a couple of large cities.
Another way to go is to wait for the Forbidden Palace and now get -20%

, but I seem to have a hard time getting it. I usually just have to hope it's close by and assume I'll take it later.
Next, go with honor. Take the policies on the right hand side (I don't know their names) and you'll end up with -33% on upgrades and +1

for every defensive building. This is huge all at once at least +14

if you're doing warmongering correctly. You'll also save tons of gold on upgrading your most excellently experienced army and navy. Defensive buildings are great too as they add numbers to your army making it easier to get peace deals and scare your enemies. The best thing about them is no maintenance costs. (Unless that's something they "fixed" in this patch too). That, and +10% combat for having troops next to one another and +1

per unit that is fortified in a city. Now, go and do that voodoo that you do so well and make your enemies pay for thinking your army is smaller than theirs.
By the time you're done with that, you should be ready for autocracy. (Make sure you're in the industrial era) Get to the upgrade that gives you +3

for every courthouse. At that point, you'll get a massive

dump. If you have captured 15 cities, that's +45

all at once around the time you're researching fertilizer. Watch your cities go from around size 12-7 to around 18-12. Now you're cooking with gas production wise.
Coming up to the end of the game,
Abandon autocracy. You may be tempted to go for double resources, but there's probably no need. If your aluminum sources are dire and you have no way of getting more, bribe or attack a city state. You'll never even need nukes. Stealth bombers/jet fighters and rocket artillery will finish the job. Go to rationalism and take the ones on the right that get you +1

for each university and public school. And now the game is over as you have just likely gained another + 20-30

from your massive sprawling empire.
And win.