I'm still a newb here, but I was told that the flow should be creating cross currents of some sort.
I only have two powerheads, one is the return from my sump and the other from a koralia. They're on 2 different sides of the tank. I have the koralia pointing slightly upwards and diagonal and I have the the powerhead from the sump pointed kind of straight off the back, but downwards so that it hits my rock. I guess it would create a sort of "L" shaped flow.
I have no clue if this is right or not, or if there's even a right or wrong.