Miz, everyone does it differently, I have the same shape as you just larger scale. To keep water movement good on the top and no "icky build up" in the corners, as well as good movement in the tank I have my pumps on the side where my output is. Pumps and output in the same directions or towards the glass side (closest).
Only on that side then the overflow is more on the other side altogether. So its kinda making a little whirlpool. If this makes since, I hope it helps.