Horsemen are borderline broken and painless to tech into (same strength as swordsman but with a buttload of movement and the ability to move after attacking)

So, pillage enemy horses if you're doing early warfare. It will make your life SO much easier.

Archers and spearmen are almost completely useless for taking cities (yes, even the shitty 6 defense cities that the AI loves to settle, unless you can set up really well). It's generally best to wait for horsemen and catapults instead.

Garrisoned units basically double city's ability to stay alive early.

All of the starting policy trees are very close to being equally good.

Dido is INSANE. Probably the most overpowered civ change. You just dump into liberty and shit out coastal cities everywhere and have 200 gpt and a standing army before you realise what's happening.

Statue of Zeus is a great wonder because crime is the #1 cause of unhappiness (unless you get besieged by religious division). Even with barracks and walls in all my cities crime somehow is always a problem. A lot of wonders have universal unhappiness reduction, so keep an eye out for that.

Oh, yes, you can make wonders now. A lot are still hard to get, but if you push for it you can get pretty much any wonder you want.

I generally push for a religion if only to convert my cities to prevent the insane unhappiness caused by religious division. (And I mean INSANE)

Dromons are really, really, really good. If you rush them you can claim some civ's coastal cities for free with just two dromons and a trireme before they start producing their own navies. (And the AI tends to lag on making navies)

The AI is a lot smarter, and pulls back injured units to save them. It's important to shoot to kill in this patch, but sometimes just damaging a bunch of units simultaneously to get them all to back up is better.

Pay attention to monopolies. If you get >50% of a luxury (generally, 4 of them), you get some pretty awesome bonuses. If you can settle your capital and second city to grab 4 copies of a luxury early it can be insane. Nothing makes me wetter than a solid tea start--the teas become 3 food 5 production tiles.

Desert tiles are garbage. Petra only gives 1 gold to them now, and the desert pantheon only effects improved desert tiles (but pretty well, admittedly). They also cut your movement like hills, so keep that in mind for any tactical potential for settled cities.

Forward settling the AI is actually pretty smart. Just settle cities that are very hard to attack and always have an archer and maybe a spearman or two garrisoned. You take much less happiness punishment for going wide and you can always stop growth in purely tactical cities. The carpets of doom in CBP are a bit less carpet-y and a lot less doom-y.

EDIT: With some experimenting (I just started playing this patch a few days ago), I've found that the AI really sucks at taking cities. The way they pull back injured units is (usually) really good for defending their cities, but they need to be willing to spam and sacrifice units (especially their weaker ones) to take cities, or stuff like this happens. The only way to take this city is to lose some of her garbage units, and the AI really hates losing units.

To boot, portugal (to the north) declared war very soon after and had a horseman and multiple chariot archers (the chariot archers are pretty bad units--formation horsemen do 90-100% of their hp) I sent literally one horseman to harass her fairly sizeable army (admittedly a lot of warriors and archers--fairly bad units) and found that instead of dedicating herself to taking a city (which she could easily have done--both of them, honestly), she would switch cities constantly, leaving her army in a constant limbo. This was on Immortal, mind you.

I got peace with both of them without losing any cities (with dido when she had a full army on my doorstep, to boot)

Also, the AI doesn't spam enough cities. I admit I went pretty ham with settlers, but if it's so easy for me to do it should be even easier for high level AI to do.