It takes a long time to play, but is totally worth it. Rarely have I seen a game so well designed and balanced.
Plant capacity wins the game. Being in the lead hamstrings your ability to grow capacity. Don't pass on chances to do so.
Don't expand beyond your ability to power expecting to buy capacity in the next round. This is doubly true if you're in the lead.
It's worth it to save money on supplies when possible. Fuel is the one cost in the game that you don't earn anything directly from.
The game ends when the requisite number of cities have been built, not when the requisite number of cities have been powered. This is how you push ahead as the game leader to win: grab cities first, expecting that you won't be able to supply them all, but rather that you'll be able to supply more than your opponents who have been left behind.
When the step 3 card comes up, players will be able to take the third spot in each city on that turn. Try to stockpile money in expectation.