Tigris & Euphrates is a difficult-to-master game with many layers of strategy, and it took me several plays to even begin to feel like I was getting the hang of it.
Of the strategy articles on BGG, I thought that this one was the most helpful and insightful. The section on "bluffing" is cute, but the section on "10 things not to do" is very good.
A short summary of some of my favorite points:
- Don't get emotionally invested in a kingdom, considering it "yours." Make what use of it you can but don't fight too hard for what is no longer of use.
- Don't forget that your weakest color is the one you need to shore up. Fifty black points won't help if you have only four blue.
- The calamity tiles are powerful for unseating leaders and setting up external conflicts you can win. If you see a good opportunity to use one, take it.
- Without a very good reason, don't start an external conflict that you're not involved in. You give one player a giant windfall.
- Watch your opponents' monuments carefully, and look for an opportunity to build one yourself, especially in the late game. A late-game monument can provide a large 2-point swing every turn if it's built in a player's two weakest colors.
- Don't leave a spot adjacent to lots of red tiles blank. It invites your opponents to drop a leader there.
Even better, although it will take a bit longer to digest, is this complete game, with strategy annotations at every move. (Part 1) (Part 2)