Ahh, I was just kidding. Shared dreaming isn't proven yet. However, I do have a way to induce a - fake - shared dream.

First, we have two people, say, Alice and Bob. Alice and Bob discuss in very great detail how the dream world will look like. Then they invent every single DC in the world. Yes, this is not Inception, you CAN design the DCs. Or simply eliminate the DCs. Then they actually write a script for their conversation in the dream and what they do. It should be at least as detailed as one for a movie. Finally, Alice and Bob go to sleep and act out their parts of the script while imagining the other person doing so too. You get a shared dream.

Seriously, that isn't a very good way to do shared dreaming, nor is it a fun way.