General Tips
Try to prepare for the future tiles. It is good to have at least one column you can finish with Lookout.
Always check how many tiles each player need to finish the game. Don't start big column if you cannot finish it and instead finish smaller one.
Monkey
Some tiles score when you play them, some score at the end of the game. So when you play the monkey, it's often better to flip a tile that has already scored and cannot provide any more benefit, and not to flip a tile that will score points at the end of the game.
For example, a good use of the monkey is on the Gunner. You will not lose the money from Gunner and you can play more Gunners and Carpenters. You also can turn the Gunner back over for another 5pts.