I find what works best is to say what I plan to do or have noticed, and just hope my partner takes the hint.
Say my partner won't take the net and is getting trapped in the back corner. I will wait for my turn to receive, then I will say, "boy, they are going to kill us if I stay back. I am coming in on my return." then when I do it and it works, I say, "Yup, that's the secret. We can win points if we come in."
If my partner still stays back . . . I guess we are going to lose.
-- Random Error Generator, Version 4.0
-- Master Moonballer