I haven't quite perfected it yet, but I find double rows of flamethrowers allow me to do maximum damage on BOTH sides of the channels I send the enemy through.
I also try to station lasers and heavy cannon at the end of rows (looking down the oncoming row of enemy) so I can (particularly with lasers) get multiple hits on a single shot.
yeah i cheated
if you want infinite money just download cheat engine, attach it to what ever browser your using, do memory searches for the exact value of the amount of money you have. then change that value and search again until you find the memory address. double click it. and edit the value to whatever.
Last night I started playing this game at 9:30 planning on playing for 30 minutes or so before getting some stuff done I had to do before going to bed. Next thing I know I look at my clock and it is 1 am.