Focus on raising your income early in the game... a in the first turn is worth anywhere from $15-$18 by the end of the game!
Be careful not to get too much population too fast, as you'll start to run into Red Lines faster and slow down your progress before you have a chance to build up a solid Incomeand Reputation infrastructure of tiles.
Keep both the public Goals and your private Goal in mind at all times; these are worth a lot at the end of the game.
Review the Tile List so you know what tiles might show up in each Stack.
When discarding a tile, look at what your opponents (particularly the player to your left) might need...it might be worth some extra money to get rid of a tile that's perfect for him.
Always pay attention to where your Population Square is relative to the Red Lines. Sometimes a single extra point can be costly in the long run.
Income and Reputation increases (or decreases) change in value during the game. The approximate number of turns left in the game (each game has about 15-18 turns in total) is the value when the tile is placed, so early game increases are worth a lot more than late game increases.