I came up with this one at random during a clinic with my older students. As always, I told them if they were going to miss, miss long. In other words, avoid hitting into the net.
As further encouragement to avoid the net, I established a new rule: anyone hitting into the net must exchange their full size racquet for my 21" Sponge Bob racquet for the next point.
This elicited exactly the responses I was hoping for: anticipation by some; dread by some; wariness of the net by all. If you are going to try this, make sure your small racquet is the craziest, most colorful or, dare I say it - most baby-ish racquet you can find.