This thread, [URL="http://forums.civfanatics.com/showthread.php?t=301319']C3C Korea Regent- Any way to salvage this?[/URL] might be what you need to read. In it a player posted saves from their game, told of the issues they faced and asked for help. It is not the only thread like it, not by any means. But it was the first one I found.
The saves are still attached to the post. I would suggest downloading them, take a look around at how the game was played, and then read and study the suggestions posted back by people here at the forum.
I would also suggest browing through some of the completed Succesion Games and see how they placed their initial cities. If you plan on a lot of wars, find an Alway War (AW) Succession Game. Those games feature a lot of warfare with a lot of AI at one time, since the idea is No peace with No body at No time. Diplomacy is easy, but every tech has to be self-researched. City placement is critical, as is preserving units.
At the risk of overkill, here is a very short list of things to avoid.
Generally, do not do these four things.
Don't automate workers. Sure, it is extra work, but you can easily make better decisions about what tasks your workers should be doing than the AI. The AI will waste tons of worker turns moving them around the empire. Turns they are moving is turns they are not improving anything.
Don't build your cities too far apart. While some folks debate this issue, it is better defensively to build your cities within walking distance of each other. That means no more than two road tiles, so that Spears and Archers can walk from one city to another in one turn. Sure, every city has 21 tiles to work. But until you can build Hospitals, the largest any city can be is 12. So, try to keep your cities to a City-space-space-City pattern.
Don't build everything. If you are going to war you don't need Temples to expand your borders. After all, the purpose of war is to capture their cities and make them yours. Your core cities won't need courthouses, your furtherest cities won't benefit from them, so don't build them everywhere. Libaries and probably barracks should be in all your core cities, along with markets. But a city that is 50 tiles from the capital (generally) has no need of any improvement.
Don't build Wonders. Let the AI build them and you capture them. Much cheaper
Don't trade Luxuries, Resources or GPT too early. If you have only one trade route to a trading partner and you are supplying them with a Luxury, Resource or Gold Per Turn, and if an unfriendly AI (unfriendly to you or your trading partner, like Barbarians) happens to block that path at the end of a turn, you are held accountable for not being able to keep your part of the agreement. In turn, this makes it more expensive, if not impossible, to supply Luxuries, Resources or Gold to the AI for the rest of the game. The AI will still sell them to you, but you lose the abilty to sell them to the AI.